Among hydrocarbon bonds, the carbon atoms, which do not contain any pi (π) bond show sp3 hybridisation. The carbon atoms, that contain one pi (π) bond show sp2 and which contain two pi (π) bonds show sp-hybridisation, because pi (π) bonds do not get hybridised. Thus, (C1)=sp -hybridisation (C2)=sp2 -hybridisation (C3)=sp -hybridisation