NEET 2005 Chemistry question

The main reason for larger number of oxidation states exhibited by the actinides than the corresponding lanthanides, is :

• (A)lesser energy difference between 5f and 6d orbitals than between 4f and 5d orbitalsCorrect
• (B)larger atomic size of actinides than the lanthanides
• (C)more energy difference between 5f and 6d orbitals than between 4f and 5d orbitals
• (D)greater reactive nature of the actinides than the lanthanides