Which of the following elements belongs to the actinoid series?

Which among the following properties of lanthanoids is $NOT$ true?

The ionic radius of $La^{3+}$ is $1.06 \ \mathop{A}\limits^o$. Which of the following is the closest value for the ionic radius of $Lu^{3+}$ in $\mathop{A}\limits^o$? $(Lu = 71, La = 57)$

Compare the chemistry of the actinoids with that of lanthanoids with reference to:
$(i)$ electronic configuration
$(ii)$ oxidation states and
$(iii)$ chemical reactivity.

Which series of elements are radioactive?

Which among the following lanthanoids shows only $+3$ oxidation state?