\(\left[ Co ( ox )_{2} Br \left( NH _{3}\right)\right]^{2 -}\) i.e. \(\simeq\left[ M ( AA )_{2} ab \right]^{2-}\)
\(\rightarrow\) cis is optically active isomers and trans is optically inactive isomer
\(\rightarrow\) Hence total isomers is \(=3\)
$A: \left[ Ni ( en )_{3}\right]^{2+}, B :\left[ Ni \left( NH _{3}\right)_{6}\right]^{2+}, C :\left[ Ni \left( H _{2} O \right)_{6}\right]^{2+}$
