Which of the following statements is $NOT$ correct for $3d$ and $4f$ series electrons?

• A
  $3d$ orbital electrons exhibit more oxidation states than the $4f$ series.
• B
  The energy difference between $3d$ and $4s$ orbitals is very small.
• C
  Europium $(II)$ is more stable than Cerium $(III)$.
• D
  As we move from Scandium to Copper,the diamagnetic property in the $3d$ orbital increases.