Which of the following metal does not produce ${\mathrm{NO}}_2$ gas as a side product when it reacts with conc. ${\mathrm{HNO}}_3$ ? 

The reaction are, 

$\begin{array}{l}\mathrm{Sn}+\mathrm{Conc}. \mathrm{HNO}⟶\\ {\mathrm{SnO}}_2+{\mathrm{NO}}_2+{\mathrm{H}}_2\mathrm{O}\\ \mathrm{Pb} +\mathrm{Conc}. {\mathrm{HNO}}_3\end{array}$

$$\begin{gathered} \mathrm{Zn}+{\mathrm{HNO}}_3\to \mathrm{Zn}{\left({\mathrm{NO}}_3\right)}_2+{\mathrm{NO}}_2+{\mathrm{H}}_2\mathrm{O} \\ \mathrm{Mg} +{\mathrm{HNO}}_{3 }\to {(\mathrm{Mg} {\mathrm{NO}}_3)}_2+{\mathrm{NO}}_2+{\mathrm{H}}_{2 }\mathrm{O} \end{gathered}$$

Thus, the correct option is D.