The type of isomerism shown by the complex $\left[{\mathrm{CoCl}}_2(\mathrm{en}{)}_2\right]$ is

The type of isomerism shown by the complex $\left[{\mathrm{CoCl}}_2(\mathrm{en}{)}_2\right]$ is isomerism in geometry. Cis trans isomerism is visible in this compound. In the cis form, there are two $Cl$ ligands and two $en$ ligands right next to one another. Two $Cl$ ligands and two $en$ ligands are in direct opposition to one another in the trans form.

Therefore, C. Geometric isomerism is the right response.