(2) $\left[{Co}({CN})_{5}({NC})\right]^{-3}$ can't Show $G.I.$
(3) $\left[{Co}\left({NH}_{3}\right)_{3}\left({NO}_{2}\right)_{3}\right]$
Show fac $\&$ mer isomerism
(4) $\left[{Co}\left({NH}_{3}\right)_{4} {Cl}_{2}\right]^{\oplus}$ show cis $\&$ trans isomerism