Which of the following lanthanoids have $[Xe] 4f^x 5d^1 6s^2$ configuration in their ground state? $(x = 1-14)$

The lanthanide for which $+II$ and $+III$ oxidation states are common is:

Choose the correct option regarding the following.
Assertion: Actinides exhibit a larger number of oxidation states than lanthanides.
Reason: There is a large energy gap between $5f$,$6d$ and $7s$ sub-shells.

What are the products formed when lanthanoids $(Ln)$ react with $1$. $H_2O$ and $2$. $N_2$?

Name the members of the lanthanoid series which exhibit $+4$ oxidation state and those which exhibit $+2$ oxidation state. Try to correlate this type of behavior with the electronic configurations of these elements.

Which one amongst the following are good oxidizing agents?
$A.$ $Sm^{2+}$
$B.$ $Ce^{2+}$
$C.$ $Ce^{4+}$
$D.$ $Tb^{4+}$
Choose the most appropriate answer from the options given below: