The salt whose aqueous solution will turn blue litmus to red is

Reaction :

$\underset{\text{W.B}}{2{\text{NH}}_{\text{4}}\text{OH}\left(\text{aq}\right)}+\underset{\text{S.A}}{{\text{H}}_{\text{2}}{\text{SO}}_{\text{4}}\left(\text{aq}\right)}\to \underset{\text{Acidic\hspace{0.17em}salt}}{{\left({\text{NH}}_{\text{4}}\right)}_{\text{2}}{\text{SO}}_{\text{4}}}+2{\text{H}}_{\text{2}}\text{O}$

* Acidic solution turn blue to RED.