The correct option is D All of the above
(a) Smaller the size of the atom, smaller is the covalent radius and hence smaller the covalent bond.
(b) Greater the s-character, more bulky the orbitals and hence smaller the bond length.
(c) Greater the bond order, smaller the bond length. Triple bond is shorter than a double bond and a double bond is shorter than a single bond.
Hence, all the statements are correct.