By which organic compound all the oils are known ?

Answer: Option C

Hydrocarbons are organic compounds containing carbon and hydrogen and found in crude oil and natural gas. Hydrocarbons are formed from the remains of marine animals and plants that lived in shallow inland seas, died, and drifted to the bottom. The term petroleum is used as a common denotation for crude oil (mineral oil) and natural gas, i.e., the hydrocarbons from which various oil and gas products are made.