The standard potentials at 298K for the following half reactions are given against each :$\begin{array}{1 1}Zn^{2+}(aq)+2e^-\leftrightharpoons Zn(s)\quad-0.762V&2H^+(aq)+2e^-\leftrightharpoons Cr(s)\quad 0.000V\\Cr^{3+}(aq)+3e^-\leftrightharpoons Cr(s)\quad -0.740V&Fe^{3+}(aq)+2e^-\leftrightharpoons Fe^{2+}(aq)\quad 0.770V\end{array}$.Which is the strongest reducing agent?

Question

$\begin{array}{1 1}Zn(s)\\Cr(s)\\H_2(g)\\Fe^{2+}\end{array} $