Answer is: (4) compounds with different boiling points.
Gasoline consists of hydrocarbons with between four and twenty carbon atoms.
Gasoline is a mixture of many different hydrocarbons: alkanes (paraffins), cycloalkanes and alkenes (olefins).
Petroleum is mixture (solution) consist of several different hydrocarbons (alkanes, alkenes...).
This hydroalkanes can be separated from mixture (crude oil) using distilation (usually fractional distillation), because they have different boiling points.
