In $\mathrm{d}$-Block when atomic size of one series are compared with those of corresponding element in other series :-
(I) Increase from the first $\left(3\mathrm{d}\right)$ to second $\left(4\mathrm{d}\right)$ series
(II) Increase from the second $\left(4\mathrm{d}\right)$ to third $\left(5\mathrm{d}\right)$ series
(III) Virtually the same as first $\left(3\mathrm{d}\right)$ and in second $\left(4\mathrm{d}\right)$ series
(IV) Virtually the same as second $\left(4\mathrm{d}\right)$ and in third $\left(5\mathrm{d}\right)$ series

Given below are two statements :

Statement I : The $\mathrm{E}°$ value of ${\mathrm{Ce}}^{4+}/{\mathrm{Ce}}^{3+}$ is $+1.74 \mathrm{V}$

Statement II : Ce is more stable in ${\mathrm{Ce}}^{4+}$ state than ${\mathrm{Ce}}^{3+}$ state.

In the light of the above statements, choose the most appropriate answer from the options given below:

Read the following statements and choose the correct option.
(i) $\mathrm{f}$-block elements of $6^{\text{th }}$ period are called lanthanoids.
(ii) $\mathrm{f}$-block elements of $7^{\text{th }}$ period are called actinoids.