In which of the following molecule all the carbon-carbon bonds are not equal.

[Step 1]:In option 1) Ethane H3C−CH3  contain one C-C bond.[Step 2]:In option 2) Propane H3C−CH2−CH3 all three carbons are SP3 and are equal.[Step 3]:In option 3) Propene has one c-c and c=c,hence two different bond length[Step 4]:In option 4) In this compound all the carbons are equivalent