Which one of the following is Greenhouse Gas?

The correct answer is Option (3) → Methane

A greenhouse gas lets sunlight pass through but absorbs the heat (infrared radiation) that the Earth gives off, and so keeps the lower atmosphere warm. Methane (\(\mathrm{CH_4}\)), given off by paddy fields, cattle, marshes and landfills, is one of the main greenhouse gases, along with carbon dioxide, water vapour and nitrous oxide.

Oxygen, nitrogen and hydrogen are molecules made of two identical atoms; such molecules do not absorb infrared radiation, so they are not greenhouse gases, even though nitrogen and oxygen make up about 99% of the air.