Which of the following statements is incorrect for sigma and π -bonds formed between two carbon atoms?
a. Sigma-bond is stronger than a π -bond
b. Bond energies of sigma and π -bonds are of the order of 264 kJ/mol and 347 kJ/mol
c. Free rotation of surrounding atoms about a sigma-bond is allowed but not in case of a π -bond
d. Sigma-bond determines the direction between carbon atoms but a π -bond has no primary effect in this regard