Which statement best describes the greenhouse effect and major human-caused greenhouse gases?

• A. It traps infrared radiation; major gases include CO2, CH4, N2O, and fluorinated gases
• B. Greenhouse gases reflect solar radiation away from Earth
• C. Greenhouse effect is caused by depletion of ozone in the stratosphere
• D. Water vapor has no role in the greenhouse effect

Answer: (A)

The main idea is that the greenhouse effect happens when certain gases in Earth's atmosphere absorb infrared radiation emitted by the surface and re-emit heat in all directions, trapping warmth near the planet. The best choice describes this infrared trapping and lists the major human-caused greenhouse gases: carbon dioxide, methane, nitrous oxide, and fluorinated gases, which come from burning fossil fuels, agriculture, industry, and refrigerants. That combination captures both the mechanism and the sources, making it the correct description. The notion that greenhouse gases reflect solar radiation away is not how heat is trapped—the issue is heat that has already been emitted by the surface, not sunlight being reflected. Depletion of ozone in the stratosphere is a different issue tied to UV shielding and has a separate climate impact, not the core infrared-absorption process. Water vapor does contribute to warming, but its amount is largely a response to temperature and other gases, not a direct emission control, so saying it has no role would be misleading.