The fewer the carbon atoms, the closer it is to being a gas. The only one you have to check out is A which is hexane. You know that gasoline at the pumps has 8 carbons and its a liquid. So B and C are both not gases because they are above 8.
C6 (hexane) is a liquid at room temperature not a gas.
The answer is D. If there is a gas present, it must be C3
