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Background radiation is defined as ionizing radiation present in the environment exclusively from artificial sources.
Answer: False
Explanation: Background radiation encompasses radiation from both natural and artificial origins.
The International Atomic Energy Agency (IAEA) defines background radiation as the dose attributable to all sources EXCEPT the one being specifically measured.
Answer: True
Explanation: This definition is crucial for accurately measuring the dose from a specific source by accounting for the ambient radiation present.
In radiation metrology, background radiation refers to the ambient ionizing radiation from all environmental sources.
Answer: False
Explanation: In radiation metrology, background radiation specifically refers to incidental radiation affecting the measurement of a sample, which is then subtracted.
In radiation metrology, background radiation refers to the ambient ionizing radiation from all environmental sources.
Answer: False
Explanation: In radiation metrology, background radiation specifically refers to incidental radiation affecting the measurement of a sample, which is then subtracted.
In environmental monitoring, background radiation refers specifically to incidental radiation affecting the measurement of a sample.
Answer: False
Explanation: In environmental monitoring, background radiation refers to the ambient radiation from all sources. The specific definition for incidental radiation affecting sample measurement applies more to radiation metrology.
In a radiation metrology laboratory, what does 'background radiation' specifically refer to?
Answer: Radiation from incidental sources affecting the instrument's measurement of a specific sample.
Explanation: In metrology, background is the measured ambient radiation that must be subtracted to isolate the signal from the sample itself.
In environmental monitoring, background radiation refers to:
Answer: The ambient ionizing radiation present in the environment from all sources.
Explanation: In environmental monitoring, background radiation encompasses all ambient ionizing radiation, regardless of source.
In environmental monitoring, background radiation refers to:
Answer: The ambient ionizing radiation present in the environment from all sources.
Explanation: In environmental monitoring, background radiation encompasses all ambient ionizing radiation, regardless of source.
Natural sources of background radiation include cosmic rays and radioactivity from naturally occurring materials in the environment.
Answer: True
Explanation: Cosmic radiation and terrestrial radioactivity are primary natural contributors to background radiation.
Radon and radium found in soil and rocks are considered artificial sources of background radiation.
Answer: False
Explanation: Radon and radium are naturally occurring radioactive elements found in soil and rocks, contributing to natural background radiation.
Potassium, Uranium, and Thorium are the major radionuclides of concern for terrestrial background radiation.
Answer: True
Explanation: These elements and their decay products are significant contributors to terrestrial background radiation.
The activity of primordial radionuclides like Uranium-238 has increased since the Earth's formation due to ongoing nuclear processes.
Answer: False
Explanation: Due to their long half-lives, primordial radionuclides like Uranium-238 have decreased in activity since Earth's formation.
Airborne radon is identified as the most significant source of natural background radiation exposure for humans.
Answer: True
Explanation: Radon gas, emanating from the ground, is a major contributor to inhaled radiation dose.
Modern, well-ventilated homes significantly increase the risk of radon accumulation indoors.
Answer: False
Explanation: Poorly ventilated or sealed homes are more prone to radon accumulation, not modern, well-ventilated ones.
Radon is considered the leading cause of lung cancer globally, surpassing smoking.
Answer: False
Explanation: Radon is the second leading cause of lung cancer, with smoking being the primary cause.
Cosmic radiation originates from Earth's core and primarily consists of electrons.
Answer: False
Explanation: Cosmic radiation originates from outer space and consists mainly of high-energy charged particles, not electrons from Earth's core.
Exposure to cosmic radiation decreases significantly as altitude increases.
Answer: False
Explanation: Exposure to cosmic radiation increases with altitude due to reduced atmospheric shielding.
Airline crews and frequent passengers experience higher cosmic radiation doses due to the altitudes they travel.
Answer: True
Explanation: Higher altitudes offer less atmospheric shielding, leading to increased cosmic radiation exposure for those who travel frequently by air.
Cosmic rays interacting with the atmosphere generate cosmogenic nuclides like Carbon-14 through processes other than elemental transmutation.
Answer: False
Explanation: The interaction of cosmic rays with atmospheric nuclei causes elemental transmutation, producing cosmogenic nuclides like Carbon-14.
Radiocarbon dating utilizes the constant production and incorporation of Carbon-14 into organic matter.
Answer: True
Explanation: The principle of radiocarbon dating relies on the continuous atmospheric production of Carbon-14 and its subsequent uptake by living organisms.
Potassium-40 and Carbon-14 are radioactive isotopes of essential elements that contribute significantly to internal radiation dose.
Answer: True
Explanation: These isotopes are naturally present in the body and contribute to internal dose.
The global average internal dose from radionuclides other than radon is primarily from Carbon-14.
Answer: False
Explanation: Potassium-40 and Uranium/Thorium series contribute more significantly to the global average internal dose than Carbon-14.
Cosmic radiation originates from Earth's core and primarily consists of electrons.
Answer: False
Explanation: Cosmic radiation originates from outer space and consists mainly of high-energy charged particles, not electrons from Earth's core.
Exposure to cosmic radiation decreases significantly as altitude increases.
Answer: False
Explanation: Exposure to cosmic radiation increases with altitude due to reduced atmospheric shielding.
Airline crews and frequent passengers experience higher cosmic radiation doses due to the altitudes they travel.
Answer: True
Explanation: Higher altitudes offer less atmospheric shielding, leading to increased cosmic radiation exposure for those who travel frequently by air.
Cosmic rays interacting with the atmosphere generate cosmogenic nuclides like Carbon-14 through processes other than elemental transmutation.
Answer: False
Explanation: The interaction of cosmic rays with atmospheric nuclei causes elemental transmutation, producing cosmogenic nuclides like Carbon-14.
Radiocarbon dating utilizes the constant production and incorporation of Carbon-14 into organic matter.
Answer: True
Explanation: The principle of radiocarbon dating relies on the continuous atmospheric production of Carbon-14 and its subsequent uptake by living organisms.
Potassium-40 and Carbon-14 are radioactive isotopes of essential elements that contribute significantly to internal radiation dose.
Answer: True
Explanation: These isotopes are naturally present in the body and contribute to internal dose.
The global average internal dose from radionuclides other than radon is primarily from Carbon-14.
Answer: False
Explanation: Potassium-40 and Uranium/Thorium series contribute more significantly to the global average internal dose than Carbon-14.
The primary contributors to internal radiation dose from biologically functional components are isotopes of elements like Calcium and Sodium.
Answer: False
Explanation: Potassium and Carbon isotopes are the primary contributors among biologically functional elements.
The majority of the natural neutron background radiation originates from radioactive decay within the Earth's crust.
Answer: False
Explanation: Natural neutron background radiation primarily originates from cosmic ray interactions with the atmosphere.
Which radionuclides are identified as the primary concerns for terrestrial background radiation?
Answer: Potassium, Uranium, and Thorium
Explanation: These elements and their decay products are the principal sources of terrestrial radioactivity contributing to background radiation.
What has happened to the activity of primordial radionuclides like Uranium-238 since the Earth's formation?
Answer: It has decreased significantly due to radioactive decay.
Explanation: Primordial radionuclides have been decaying since Earth's formation, resulting in a decrease in their activity over geological time.
What is identified as the single biggest source of natural background radiation exposure for humans?
Answer: Airborne radon gas
Explanation: Inhaled radon and its decay products constitute the largest component of natural background radiation dose to the general population.
What is the primary health risk associated with inhaling radon gas?
Answer: Lung cancer
Explanation: Inhaled radon decay products can damage lung tissue, significantly increasing the risk of developing lung cancer.
How does altitude generally affect exposure to cosmic radiation?
Answer: Exposure increases as altitude increases.
Explanation: Higher altitudes have less atmospheric shielding, resulting in greater exposure to cosmic radiation.
Why is cosmic radiation a particular concern for airline crews and frequent passengers?
Answer: They travel at altitudes where cosmic radiation intensity is significantly higher.
Explanation: Flight altitudes are within the region of increased cosmic ray intensity due to reduced atmospheric shielding.
The process by which cosmic rays interact with atomic nuclei in the atmosphere to create new radioactive isotopes is called:
Answer: Elemental transmutation
Explanation: Cosmic ray interactions can alter the atomic nuclei of atmospheric elements, creating new isotopes.
What is the primary application of Carbon-14 produced by cosmic rays?
Answer: Radiocarbon dating
Explanation: The known production rate and decay of Carbon-14 make it invaluable for dating organic materials.
Which essential elements' radioactive isotopes contribute significantly to internal radiation dose in the human body?
Answer: Potassium and Carbon
Explanation: Potassium-40 and Carbon-14 are naturally occurring radioactive isotopes of essential elements found within the human body.
How does the Earth's geomagnetic field influence cosmic radiation exposure?
Answer: It deflects some cosmic rays, acting as a shield and causing geographical variations in exposure.
Explanation: The geomagnetic field provides partial shielding against cosmic rays, leading to variations in exposure based on latitude.
What does NORM stand for in the context of background radiation?
Answer: Naturally Occurring Radioactive Material
Explanation: NORM refers to materials containing radionuclides that are naturally present in the environment.
Which radionuclides are identified as the primary concerns for terrestrial background radiation?
Answer: Potassium, Uranium, and Thorium
Explanation: These elements and their decay products are the principal sources of terrestrial radioactivity contributing to background radiation.
What has happened to the activity of primordial radionuclides like Uranium-238 since the Earth's formation?
Answer: It has decreased significantly due to radioactive decay.
Explanation: Primordial radionuclides have been decaying since Earth's formation, resulting in a decrease in their activity over geological time.
What is identified as the single biggest source of natural background radiation exposure for humans?
Answer: Airborne radon gas
Explanation: Inhaled radon and its decay products constitute the largest component of natural background radiation dose to the general population.
What is the primary health risk associated with inhaling radon gas?
Answer: Lung cancer
Explanation: Inhaled radon decay products can damage lung tissue, significantly increasing the risk of developing lung cancer.
How does altitude generally affect exposure to cosmic radiation?
Answer: Exposure increases as altitude increases.
Explanation: Higher altitudes have less atmospheric shielding, resulting in greater exposure to cosmic radiation.
Why is cosmic radiation a particular concern for airline crews and frequent passengers?
Answer: They travel at altitudes where cosmic radiation intensity is significantly higher.
Explanation: Flight altitudes are within the region of increased cosmic ray intensity due to reduced atmospheric shielding.
The process by which cosmic rays interact with atomic nuclei in the atmosphere to create new radioactive isotopes is called:
Answer: Elemental transmutation
Explanation: Cosmic ray interactions can alter the atomic nuclei of atmospheric elements, creating new isotopes.
What is the primary application of Carbon-14 produced by cosmic rays?
Answer: Radiocarbon dating
Explanation: The known production rate and decay of Carbon-14 make it invaluable for dating organic materials.
Which essential elements' radioactive isotopes contribute significantly to internal radiation dose in the human body?
Answer: Potassium and Carbon
Explanation: Potassium-40 and Carbon-14 are naturally occurring radioactive isotopes of essential elements found within the human body.
How does the Earth's geomagnetic field influence cosmic radiation exposure?
Answer: It deflects some cosmic rays, acting as a shield and causing geographical variations in exposure.
Explanation: The geomagnetic field provides partial shielding against cosmic rays, leading to variations in exposure based on latitude.
What does NORM stand for in the context of background radiation?
Answer: Naturally Occurring Radioactive Material
Explanation: NORM refers to materials containing radionuclides that are naturally present in the environment.
Medical X-rays and fallout from nuclear weapons testing are classified as natural sources of background radiation.
Answer: False
Explanation: Medical procedures and nuclear weapons testing are significant sources of artificial background radiation.
Atmospheric nuclear explosions between the 1940s and 1960s led to a significant global increase in background radiation.
Answer: True
Explanation: These tests dispersed radioactive isotopes globally, temporarily elevating background radiation levels.
The Limited Test Ban Treaty of 1963 prohibited underground nuclear tests, leading to a decrease in background radiation.
Answer: False
Explanation: The treaty prohibited above-ground tests, which were the primary source of atmospheric radioactive fallout, thus leading to a decrease in background radiation.
Inhabitants near the Fukushima I nuclear accidents received total doses generally exceeding 50 mSv.
Answer: False
Explanation: Doses received by inhabitants near Fukushima were generally below 50 mSv, with thyroid doses for children reported below 50 mSv.
A typical chest X-ray delivers an effective dose of approximately 20 mSv.
Answer: False
Explanation: A typical chest X-ray delivers an effective dose of approximately 20 µSv (microsieverts), not 20 mSv.
The effective dose from a whole-body CT scan is significantly lower than that of a chest X-ray.
Answer: False
Explanation: A whole-body CT scan delivers a significantly higher effective dose, ranging from 1 to 20 mSv, compared to a chest X-ray.
Atmospheric nuclear explosions between the 1940s and 1960s led to a significant global increase in background radiation.
Answer: True
Explanation: These tests dispersed radioactive isotopes globally, temporarily elevating background radiation levels.
The Limited Test Ban Treaty of 1963 prohibited underground nuclear tests, leading to a decrease in background radiation.
Answer: False
Explanation: The treaty prohibited above-ground tests, which were the primary source of atmospheric radioactive fallout, thus leading to a decrease in background radiation.
Inhabitants near the Fukushima I nuclear accidents received total doses generally exceeding 50 mSv.
Answer: False
Explanation: Doses received by inhabitants near Fukushima were generally below 50 mSv, with thyroid doses for children reported below 50 mSv.
A typical chest X-ray delivers an effective dose of approximately 20 mSv.
Answer: False
Explanation: A typical chest X-ray delivers an effective dose of approximately 20 µSv (microsieverts), not 20 mSv.
The effective dose from a whole-body CT scan is significantly lower than that of a chest X-ray.
Answer: False
Explanation: A whole-body CT scan delivers a significantly higher effective dose, ranging from 1 to 20 mSv, compared to a chest X-ray.
Cigarettes contain polonium-210, a decay product of radon, which can lead to significant localized radiation dose in the lungs for heavy smokers.
Answer: True
Explanation: Polonium-210 in tobacco smoke can result in substantial localized radiation dose to lung tissues.
Coal burning contributes to background radiation by releasing radioactive materials like uranium and thorium into the environment as fly ash.
Answer: True
Explanation: Coal combustion releases naturally occurring radioactive materials present in coal into the atmosphere.
What was the approximate peak worldwide increase in background radiation per year due to atmospheric nuclear testing?
Answer: 0.15 mSv
Explanation: The global average dose rate from atmospheric nuclear testing peaked around 1963 at approximately 0.15 mSv per year.
What was the effect of the Limited Test Ban Treaty of 1963 on background radiation?
Answer: It prohibited above-ground tests, leading to a decrease in radiation from this source.
Explanation: By banning atmospheric tests, the treaty significantly reduced the release of radioactive fallout into the environment.
Which major civilian nuclear accident is noted for causing immediate deaths due to acute radiation syndrome?
Answer: Chernobyl accident
Explanation: The Chernobyl disaster resulted in immediate fatalities from acute radiation syndrome among first responders.
What is the approximate effective dose from a typical chest X-ray?
Answer: 20 µSv
Explanation: A standard chest X-ray delivers a relatively low effective dose of approximately 20 microsieverts.
How does the effective dose from a whole-body CT scan compare to that of a chest X-ray?
Answer: It is significantly higher, ranging from 1 to 20 mSv.
Explanation: CT scans involve higher radiation doses than conventional X-rays due to the multiple images acquired.
What radioactive substance found in cigarettes contributes to lung radiation dose?
Answer: Polonium-210
Explanation: Polonium-210, a decay product of radon, accumulates in tobacco leaves and contributes to lung dose when inhaled.
What is the significance of the 'bomb pulse' concerning Carbon-14?
Answer: It describes the sharp increase in atmospheric Carbon-14 levels caused by nuclear weapon tests.
Explanation: The 'bomb pulse' refers to the temporary but significant elevation of atmospheric Carbon-14 concentrations resulting from nuclear weapons testing.
Which of the following is classified as an artificial source of background radiation?
Answer: Medical procedures like X-rays and CT scans
Explanation: Medical diagnostics represent a significant source of artificial background radiation exposure.
What is the significance of the 'bomb pulse' concerning Carbon-14?
Answer: It describes the sharp increase in atmospheric Carbon-14 levels caused by nuclear weapon tests.
Explanation: The 'bomb pulse' refers to the temporary but significant elevation of atmospheric Carbon-14 concentrations resulting from nuclear weapons testing.
The primary unit used globally to measure human exposure to ionizing radiation is the Gray (Gy).
Answer: False
Explanation: The Sievert (Sv) is the primary unit for measuring human exposure (effective dose), while the Gray (Gy) measures absorbed dose.
Globally, the average annual exposure from natural background radiation is significantly lower than that from artificial sources.
Answer: False
Explanation: Globally, natural background radiation contributes approximately four times more to average annual exposure than artificial sources.
In countries like the US and Japan, artificial radiation exposure is generally lower than natural background exposure due to limited medical imaging.
Answer: False
Explanation: In countries with high utilization of medical imaging, such as the US and Japan, artificial radiation exposure often exceeds natural background exposure.
High background radiation can make radiation protection instruments insensitive to low levels of contamination.
Answer: True
Explanation: Elevated background radiation can obscure or mask low-level radiation signals, reducing instrument sensitivity.
Geiger-Müller tubes are generally more complex and expensive than scintillation detectors for measuring radiation.
Answer: False
Explanation: Geiger-Müller tubes are typically less complex and more affordable than scintillation detectors.
The International Commission on Radiological Protection (ICRP) recommends a limit of 100 mSv per year for occupational radiation exposure.
Answer: False
Explanation: The ICRP recommends a limit of 50 mSv per year for occupational exposure.
High background radiation can make radiation protection instruments insensitive to low levels of contamination.
Answer: True
Explanation: Elevated background radiation can obscure or mask low-level radiation signals, reducing instrument sensitivity.
Geiger-Müller tubes are generally more complex and expensive than scintillation detectors for measuring radiation.
Answer: False
Explanation: Geiger-Müller tubes are typically less complex and more affordable than scintillation detectors.
The International Commission on Radiological Protection (ICRP) recommends a limit of 100 mSv per year for occupational radiation exposure.
Answer: False
Explanation: The ICRP recommends a limit of 50 mSv per year for occupational exposure.
The International Atomic Energy Agency (IAEA) primarily focuses on defining background radiation and does not provide radiation protection standards.
Answer: False
Explanation: The IAEA provides definitions and also develops and promotes radiation protection standards and safety guidelines.
The photoelectric effect can cause a small enhancement of background radiation doses near materials with low atomic numbers.
Answer: False
Explanation: The photoelectric effect is more pronounced with high atomic number materials.
The ICRP recommends a limit of 1 mSv per year for public exposure to artificial radiation sources.
Answer: True
Explanation: This limit is a key recommendation for protecting the general public from artificial radiation sources.
What is the most commonly used unit to measure annual human exposure to ionizing radiation?
Answer: Millisievert (mSv)
Explanation: The millisievert (mSv) is the standard unit for effective dose, representing biological risk from radiation exposure.
How does the global average annual exposure from natural background radiation compare to that from artificial sources?
Answer: Natural exposure is approximately four times higher than artificial exposure.
Explanation: Globally, natural sources contribute substantially more to average annual radiation dose than artificial sources.
In some developed countries like the US and Japan, why might artificial radiation exposure exceed natural background exposure?
Answer: Greater access to and utilization of medical imaging procedures.
Explanation: The widespread use of diagnostic medical procedures significantly increases the average artificial radiation dose in these regions.
According to the ICRP, what is the recommended annual dose limit for occupational radiation exposure?
Answer: 50 mSv
Explanation: The ICRP sets the annual occupational dose limit at 50 mSv to ensure worker safety.
What is the primary role of organizations like the ICRP and IAEA in relation to background radiation?
Answer: To develop and recommend standards for radiation protection.
Explanation: These international bodies provide foundational recommendations and standards for radiation safety and protection.
What is the ICRP's recommended annual dose limit for public exposure to artificial radiation sources?
Answer: 1 mSv
Explanation: The ICRP recommends a dose limit of 1 mSv per year for members of the public from artificial sources.
What is the most commonly used unit to measure annual human exposure to ionizing radiation?
Answer: Millisievert (mSv)
Explanation: The millisievert (mSv) is the standard unit for effective dose, representing biological risk from radiation exposure.
How does the global average annual exposure from natural background radiation compare to that from artificial sources?
Answer: Natural exposure is approximately four times higher than artificial exposure.
Explanation: Globally, natural sources contribute substantially more to average annual radiation dose than artificial sources.
In some developed countries like the US and Japan, why might artificial radiation exposure exceed natural background exposure?
Answer: Greater access to and utilization of medical imaging procedures.
Explanation: The widespread use of diagnostic medical procedures significantly increases the average artificial radiation dose in these regions.
What is the most commonly used unit to measure annual human exposure to ionizing radiation?
Answer: Millisievert (mSv)
Explanation: The millisievert (mSv) is the standard unit for effective dose, representing biological risk from radiation exposure.
How does the global average annual exposure from natural background radiation compare to that from artificial sources?
Answer: Natural exposure is approximately four times higher than artificial exposure.
Explanation: Globally, natural sources contribute substantially more to average annual radiation dose than artificial sources.
In some developed countries like the US and Japan, why might artificial radiation exposure exceed natural background exposure?
Answer: Greater access to and utilization of medical imaging procedures.
Explanation: The widespread use of diagnostic medical procedures significantly increases the average artificial radiation dose in these regions.
What is the primary role of organizations like the ICRP and IAEA in relation to background radiation?
Answer: To develop and recommend standards for radiation protection.
Explanation: These international bodies provide foundational recommendations and standards for radiation safety and protection.
What is the ICRP's recommended annual dose limit for public exposure to artificial radiation sources?
Answer: 1 mSv
Explanation: The ICRP recommends a dose limit of 1 mSv per year for members of the public from artificial sources.
Ramsar in Iran and Guarapari in Brazil are known for having exceptionally high natural background radiation levels.
Answer: True
Explanation: These locations are globally recognized for their elevated natural radiation environments.
The highest level of purely natural radiation ever recorded on Earth's surface was measured in a monazite-rich black beach in India.
Answer: False
Explanation: The highest recorded level was measured on a Brazilian black beach.
The use of radioactive limestone as a building material is the primary reason for high radiation levels in Ramsar, Iran.
Answer: True
Explanation: Radioactive building materials, including limestone and granite, contribute significantly to the elevated radiation levels in Ramsar.
Ramsar in Iran and Guarapari in Brazil are known for having exceptionally high natural background radiation levels.
Answer: True
Explanation: These locations are globally recognized for their elevated natural radiation environments.
The highest level of purely natural radiation ever recorded on Earth's surface was measured in a monazite-rich black beach in India.
Answer: False
Explanation: The highest recorded level was measured on a Brazilian black beach.
The use of radioactive limestone as a building material is the primary reason for high radiation levels in Ramsar, Iran.
Answer: True
Explanation: Radioactive building materials, including limestone and granite, contribute significantly to the elevated radiation levels in Ramsar.
The 'ship effect' describes the phenomenon where neutron flux measures higher near larger objects like ships due to their interaction with cosmic rays.
Answer: True
Explanation: This effect highlights how surrounding materials can influence radiation measurements.
Which of the following locations is known for exceptionally high natural background radiation levels?
Answer: Ramsar, Iran
Explanation: Ramsar, Iran, is recognized globally for its significantly elevated natural background radiation levels.
What was the highest level of purely natural radiation ever recorded on Earth's surface, and where was it measured?
Answer: 90 µGy/h on a Brazilian black beach
Explanation: A rate of 90 µGy/h was recorded on a monazite-rich beach in Brazil, representing the highest known purely natural radiation level.
What does the 'ship effect' refer to in the context of neutron background radiation?
Answer: Increased neutron flux near large objects like ships due to cosmic ray interactions.
Explanation: This effect describes how large objects can enhance local neutron flux through interactions with cosmic rays.
Which of the following locations is known for exceptionally high natural background radiation levels?
Answer: Ramsar, Iran
Explanation: Ramsar, Iran, is recognized globally for its significantly elevated natural background radiation levels.
What was the highest level of purely natural radiation ever recorded on Earth's surface, and where was it measured?
Answer: 90 µGy/h on a Brazilian black beach
Explanation: A rate of 90 µGy/h was recorded on a monazite-rich beach in Brazil, representing the highest known purely natural radiation level.
Preliminary studies in high natural background radiation areas like Ramsar suggest potential beneficial health effects, though more data is needed.
Answer: True
Explanation: Research in these areas is ongoing, with initial findings exploring potential adaptive responses and health impacts.
What does the 'ship effect' refer to in the context of neutron background radiation?
Answer: Increased neutron flux near large objects like ships due to cosmic ray interactions.
Explanation: This effect describes how large objects can enhance local neutron flux through interactions with cosmic rays.
Which two railroads, whose predecessors co-owned the newspaper, still have headquarters in Jacksonville?
Answer: CSX Transportation and the Florida East Coast Railway
Explanation: The successor companies to two of the original railroad owners, CSX Transportation and the Florida East Coast Railway, maintain headquarters in Jacksonville.