Which pair of substances can be combined to produce ammonia gas?

(P)  ${\left({\mathrm{NH}}_4\right)}_2{\mathrm{SO}}_4\left(s\right)$ and $\mathrm{NaOH}\left(\mathrm{aq}\right)$

(Q) ${\mathrm{NH}}_3\left(\mathrm{aq}\right)$ and ${\mathrm{HCI}}_{\left(\mathrm{aq}\right)}$

The reaction is,

${\mathrm{NH}}_3+\mathrm{HCl}⟶{\mathrm{NH}}_4\mathrm{Cl}$

The pair of substances can be combined to produce ammonia gas. Thus, the option is,

${\left({\mathrm{NH}}_4\right)}_2{\mathrm{SO}}_4\left(s\right)$ and $\mathrm{NaOH}\left(\mathrm{aq}\right)$ .