The correct option is D C3H8
Propane C3H8 is the saturated hydrocarbon. It contains all single bonds. No double or triple bond is present. A hydrocarbon contains C and H only. Hence, the options (D) and (E) are ruled out as they contain O atoms.
C2H4 contains C=C double bond and C4H6 contains C≡C triple bond or two C=C double bonds.
Hence, they are unsaturated hydrocarbons.