Larger number of oxidation states are exhibited by the actinoids than those by the lanthanoids,the main reason being

• A
  Lesser energy difference between $5f$ and $6d$ than $4f$ and $5d$ orbitals
• B
  More energy difference between $5f$ and $6d$ than between $4f$ and $5d$ orbitals
• C
  Less reactive nature of the actinoids than the lanthanoids
• D
  $4f$ orbitals are more diffused than $5f$ orbitals