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DOST Science Practice Exam

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Which gas, commonly produced by burning fossil fuels, is a major greenhouse gas?
Correct Answer:
Carbon dioxide
Explanation:
Greenhouse gases trap heat in the atmosphere. When fossil fuels burn, the carbon in the fuel combines with oxygen to form carbon dioxide. This gas is a major greenhouse gas because it efficiently absorbs infrared radiation emitted by Earth's surface and re-radiates it back downward, warming the lower atmosphere and surface. Even though some gases are more potent heat absorbers per molecule, carbon dioxide is released in much larger amounts from burning fuels, making it the dominant greenhouse gas from this process. The other options do not act as significant greenhouse gases in this context: oxygen and nitrogen are the main air components and don’t trap heat like CO2, and hydrogen isn’t present in the atmosphere in a form that contributes notably to the greenhouse effect.

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