More number of oxidation states are exhibited by the actinoids than by the lanthanoids. The main reason for this is

• A
  more active nature of the actinoids
• B
  more energy difference between $5f$ and $6d$ orbitals than that between $4f$ and $5d$ orbitals
• C
  lesser energy difference between $5f$ and $6d$ orbitals than that between $4f$ and $5d$ orbitals
• D
  greater metallic character of the lanthanoids than that of the corresponding actinoids.