Which of the following is the main component of the natural gas?

1. A

   Ethane

   Ethane is a minor component of natural gas, used after separation for chemicals. It is not the main constituent. C2 is a companion, not the bulk.

2. B

   Butane

   Butane is a heavier fraction, bottled as LPG with propane, not the bulk of pipeline natural gas. C4 is not the key.

3. C

   Carbon monoxide

   Carbon monoxide is a combustion product or coal-gas component, not the main molecule of natural gas. CO is the wrong family.

4. D

   Methane

   (d) Official key: Methane (CH4) is the main component of natural gas. Pipeline gas is mostly methane with smaller ethane, propane and inerts. Among the four, methane is the official bulk gas.

Summary. Official key is (d). Natural gas is chiefly methane. Ethane and butane are lesser alkanes; carbon monoxide is not the reservoir gas. Keep methane. The official letter is (d).