Which of the following is a greenhouse gas? (4 points)
oxygen
hydrogen
nitrogen
water vapor

Water Vapor. As a greenhouse gas, the higher concentration of water vapor is then able to absorb more thermal IR energy radiated from the Earth, thus further warming the atmosphere. The warmer atmosphere can then hold more water vaporand so on and so on. This is referred to as a 'positive feedback loop'.

Ithink your answer is b