The correct option is C Methane
Methane is a potent "greenhouse gas," more than 20 times more effective at trapping heat, than carbon dioxide. Methane in the atmosphere tends to slowly react with oxygen over time, forming methanol, formaldehyde, or formic acid. These chemicals contribute to the formation of smog and upper atmosphere "aerosols". These methane breakdown products may then be further oxidized into carbon dioxide and water.