This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Environment and health, Subject name: Social & Preventive Medicine
Greenhouse gases are called as such because they - 
Select and explain. 
A. Are used in warming plant growth chambers, B. Help inmaintaining atmosphereic O2 and CO2 balance, C. Ar produced by green photosynthesizing plants and are trapped in the eah's atmosphere, D. Prevent the escape of heat waves reradiated from the eah's surface
D: Prevent the escape of heat waves reradiated from the eah's surface
Answer: D: Prevent the escape of heat waves reradiated from the eah's surface 
Explanation: A greenhouse gas (sometimes abbreted GHG) is a gas that absorbs and emits radiant energy within the thermal infrared range. Greenhouse gases cause the greenhouse effect. The primary greenhouse gases in Eah's atmosphere are water vapor, carbon dioxide, methane, nitrous oxide and ozone. Without greenhouse gases, the average temperature of Eah's surface would be about -18 degC (0 degF), rather than the present average of 15 degC (59 degF). The atmospheres of Venus, Mars and Titan also contain greenhouse gases. Ref : https://en.m.wikipedia.org/wiki/Greenhouse_gas