Dissolution of which of the following in water is endothermic?

Ammonium chloride dissolves in water having an endothermic reaction. This is because of entropy change. In this case, $\Delta S$ is positive.

$${\mathrm{NH}}_4\mathrm{Cl}\left(aq\right)\to {\mathrm{NH}}_4^{\oplus }\left(aq\right)+C{l}^{\ominus }\left(aq\right)$$

The ions that were held together in the crystalline solid are free and move in all possible directions. Its entropy increases and then $T\Delta S>\Delta H$.

Hence the correct answer is (D) ${\mathrm{NH}}_4\mathrm{Cl}$.