Correct option (d) Am
Explanation :
'La' forms compounds in which its oxidation no. is +3. 'Eu' and 'Gd' exhibit +2 as well as +3 oxidation state and not higher than that. due to stable (f7) configuration. whereas 'Am' exhibits the oxidation states +2, +3, +4, +5, +6, etc. due to extremely large size and low ionisation energy.