The lanthanide contraction is responsible for the fact that

The correct statements among the following are:
$A$. $Mo(VI)$ and $W(VI)$ are less stable than $Cr(VI)$.
$B$. $Ce^{4+}$ and $Tb^{4+}$ are oxidants, while $Eu^{2+}$ and $Yb^{2+}$ are reductants.
$C$. $Cm$ and $Am$ have seven unpaired electrons.
$D$. Actinoid contraction is greater from element to element than lanthanoid contraction.
Choose the correct answer from the options given below:

Which lanthanoid from the following may exhibit $+4$ oxidation state with $f^{0}$ configuration?

Europium is

Transuranium elements are

If the ionic radius of $_{57}La^{3+}$ is $1.06 \ \mathring{A}$,then the ionic radius of $_{71}Lu^{3+}$ will be approximately close to which of the following values in $\mathring{A}$?