In the complex $\left[{\mathrm{CoCl}}_2(en{)}_2\right]\mathrm{Br}$, the co-ordination number and oxidation state of cobalt are :

$\left[{\mathrm{CoCl}}_2(en{)}_2\right]\mathrm{Br}\Rightarrow {\left[{\mathrm{CoCl}}_2(en{)}_2\right]}^{+1}$ Let x be the oxidation state of cobalt, 

$\begin{array}{l}x-2=+1\\ x=3\end{array}$

Co-ordination number = denticity of the central atom x number of ligands attached to it

Co-ordination number = 6

Hence, correct option is A.