The correct option is D All of the above.
(a) σ bond is stronger than π bond, because overlapping of atomic orbitals can take place to a greater extent during the formation of sigma bond compared to the formation of a π bond.
(b) Only p and d-orbitals can form π bonds. s - orbitals always form sigma bonds.
(c) When the orbitals of an atoms undergoes head on overlapping to form a σ bond, sharing of only two electrons are possible. For more electrons to be shared, lateral orbital overlapping takes place. So, there can be only one σ bond between two atoms.