Which of the following ligand can exhibit linkage isomerism when present in complex compound.

I) $S{O}_4^{-2}$    II) $P{O}_4^{-3}$   III) $S{O}_3^{-2}$   IV) $C{O}_3^{-2}$     V) $C{N}^{-}$    VI) $SC{N}^{-}$   VII) $C_2{O}_4^{-2}$