Calculate oxidation number of $\left[Co\right(en{)}_3]C{l}_3$.

The correct option is C 3

oxidation number of $\left[Co\right(en{)}_3]C{l}_3$ is $+3$.

$X+3\left(0\right)+3(-1)=0$

$X=+3$.

So oxidation number of $CO$ in $\left[Co\right(en{)}_3]C{l}_3$ is $+3$.