Assertion (A):  ${\mathrm{Cr}}^{2+}\left(\mathrm{aq}\right)$ is a reducing agent where has ${\mathrm{Mn}}^{3+}\left(\mathrm{aq}\right)$ is an oxidizing agent
Reason (R): ${\mathrm{Cr}}^{6+}\left(\mathrm{aq}\right),{\mathrm{M}}^{7+}\left(\mathrm{aq}\right)$ are unstable
Select the most appropriate answer from the options given below: