Which of the following statements is not true for transition elements?

Zinc and mercury do not show variable valency like $d-$block elements because

How many of the following lanthanide elements exhibit $+4$ oxidation state?
$Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy$

State whether the following statements are true or false:
$(i)$ Atomic size increases with an increase in the atomic number of elements.
$(ii)$ The electron gain enthalpy for noble gases is approximately zero.
$(iii)$ The first element of the actinoid series is $Th$ and the last element is $Lu$.
$(iv)$ The general electronic configuration of $d$-orbitals is always $(n-1)d^{1-10}ns^2$.

What metals are in German silver alloy?

Which one of the following has the maximum number of unpaired electrons?