Which of the following elements exhibits a $+4$ oxidation state?

Which of the following elements is a lanthanide (Rare–earth element)?

The atomic number of cerium $(Ce)$ is $58$. The correct electronic configuration of $Ce^{3+}$ ion is

Given below are two statements:
Statement $I$: In the Lanthanoids,the formation of $Ce^{+4}$ is favoured by its noble gas configuration.
Statement $II$: $Ce^{+4}$ is a strong oxidant reverting to the common $+3$ state.
In the light of the above statements,choose the most appropriate answer from the options given below:

State the $E^o$ values of lanthanoids and provide their reactions with the following: $(i)$ $H_2$,$(ii)$ Carbon,$(iii)$ Dilute acid,$(iv)$ Halogens,$(v)$ $O_2$,and $(vi)$ $H_2O$.

Discuss the trends in oxidation states shown by actinoids.