All transition elements are $d$-block elements,but all $d$-block elements are not transition elements. Explain.

(N/A) transition element is defined as an element which has incompletely filled $d$-orbitals in its ground state or in any one of its oxidation states.
$d$-block elements are those in which the last electron enters the $d$-orbital. Their general electronic configuration is $(n-1)d^{1-10} ns^{0-2}$.
Elements like $Zn$,$Cd$,and $Hg$ have a completely filled $d^{10}$ configuration in their ground state as well as in their common oxidation states $(+2)$.
Since they do not have incompletely filled $d$-orbitals,they do not exhibit the characteristic properties of transition elements.
Therefore,while all transition elements belong to the $d$-block,elements like $Zn$,$Cd$,and $Hg$ are $d$-block elements but not transition elements.