Explanation

(c)
$Zn\ (s)\ + \ {2H}^{+}\ (aq)\ \rightarrow \ {Zn}^{2 +}(aq)\ + \ H_{2}\ (g)\$
Reaction quotient $Q\ = \frac{\left\lbrack {Zn}^{2 +} \right\rbrack}{\left\lbrack H^{+} \right\rbrack^{2}\ }$
Corresponding cell is
$\ \ \ \ \ \ \ Zn\ |\ {Zn}^{2 +}\ (C_{1})\ ||\ H^{+}\ (aq)\ |\ Pt\ (H_{2})$
-anode + cathode
and $E_{cell} = \ E_{cell}^{{^\circ}}\ - \frac{0.0591}{2}\ log\ K$
$= \ \ \ \ E_{cell}^{{^\circ}}\ - \ \frac{0.0591}{2}\log\frac{\lbrack{Zn}^{2 +}\rbrack}{\lbrack H^{+}\rbrack^{2}}$
$= \ \ \ \ E_{cell}^{{^\circ}} + \ \frac{0.0591}{2}\log\frac{\lbrack H^{+}\rbrack^{2}}{\lbrack{Zn}^{2 +}\rbrack}$
If $H_{2}{SO}_{4}$ is added to cathodic compartment, (towards reactant side), then $\mathcal{Q}$ decreases (due to increase in $H^{+}$).
Hence, equilibrium is displaced towards right and $E_{cell}$ increases.