Negatively charged monodentate strong field ligand $\left(\mathrm{X}^{-}\right)$and weak field ligand $\left(\mathrm{Y}^{-}\right)$form complexes $\left[\mathrm{MnX}_6\right]^{4-}$ and $\left[\mathrm{MnY}_6\right]^{4-}$, respectively, under certain reaction conditions. Let the crystal field spliting energy for $\left[\mathrm{MnX}_6\right]^{4-}$ and $\left[\operatorname{Mn} \mathrm{Y}_6\right]^{4-}$ be $\left(\Delta_0\right)_1$ and $\left(\Delta_0\right)_2$, respectively. The correct statement(s) is(are):

• Correct answer
  A

  Electron pairing energy in $\left[\mathrm{MnX}_6\right]^{4-}$ is smaller than $\left(\Delta_0\right)_1$.
• B

  $\left[\mathrm{MnY}_6\right]^{4-}$ is more stabilized than $\left[\mathrm{MnX}_6\right]^{4-}$.
• Correct answer
  C

  The $t_{2 g}$ orbitals in $\left[\mathrm{MnX}_6\right]^{4-}$ are stabilized by $2\left(\Delta_0\right)_1$ as compared to degenerate $d$ orbitals.
• D

  $\left[\mathrm{MnY}_6\right]^{4-}$ is intense in colour as compared to $\left[\mathrm{MnX}_6\right]^{4-}$.

Hence, the correct answer is options: 'A', 'C'.