How much is the relative contribution of methane to total global warming ? (A) 14% (B) 20% (C) 6% (D) 60%
How much is the relative contribution of methane to total global warming ? (A) 14% (B) 20% (C) 6% (D) 60%

(B) 20% 

Explanation: It compares the amount of heat trapped by a given mass of gas to the amount of heat trapped by a similar mass of carbon dioxide and is stated as a factor of carbon dioxide, a global warming potential index for methane, carbon monoxide, nitrous oxide, and CFCs relative to carbon dioxide. CO2 is the most significant contributor.