Which method will be the best for separating the gasoline from crude oil?
a- gas chromatography
b- freezing
c- filtration with a paper filter
d- distillation

I think that distillation will be the best answer. Distillation essentially boils liquids until they turn into the gaseous state and then condense the gas to increasingly purify the resulting liquid ie the process can be repeated to enhance purity. This process is used not just for petroleum but also to purify water and also for alcohol recovery.