Crystal field stabilization energy(CFSE) is zero for the octahedral complex with the configuration

• A

  ${\mathrm{d}}^5$(weak field ligand)

• B

  ${\mathrm{d}}^5$(strong field ligand)

• C

  ${\mathrm{d}}^6$(weak field ligand)

• D

  ${\mathrm{d}}^6$(strong field ligand)