Chemistry - Complete d-block Question with Solution | TestHub

The correct answer is (D).

Transition elements are defined as elements that possess a partially filled $d$-subshell in their elemental form or in any of their common ionic states.

Zinc (Zn), Cadmium (Cd), and Mercury (Hg) have a general electronic configuration of $(n-1)d^{10}n{s}^2$. In their ground states, as well as their common $+2$ oxidation states ($(n-1)d^{10}n{s}^0$), their $d$-subshell remains completely filled.

Since this $d$-subshell belongs to the penultimate shell ($(n-1)$th shell), this entire inner shell remains completely filled ($s^2{p}^6{d}^{10}$) in both ground and higher oxidation states.