Which of the following elements is not an actinoid?

Consider the following two statements:
$Statement-I:$ Among $Mg, Al, Mg^{2+}, Al^{3+}$,the one having the smallest size is $Al^{3+}$.
$Statement-II:$ $Eu$ has an exceptionally high atomic radius among lanthanide elements.
The correct answer is:

The atomic size decreases with an increase in atomic number for the elements of the ........

Which actinoid from the following in its $+3$ state has the largest size?

The electronic configurations of bivalent europium and trivalent cerium are
(atomic number : $Xe=54, Ce=58, Eu=63$ )

Which of the following forms a stable $+4$ oxidation state?