Which of the following metals will not release $H_{2(g)}$ upon reaction with an acid?

The standard hydrogen electrode has a zero electrode potential because .....

The $E^o$ values of half-cells are given below. Which combination of two half-cells will form a cell with the maximum potential?
$(i)$ $A + e^- \rightarrow A^- ; E^o = -0.24 \ V$
$(ii)$ $B^- + e^- \rightarrow B^{2-} ; E^o = +1.25 \ V$
$(iii)$ $C^- + 2e^- \rightarrow C^{3-} ; E^o = -1.25 \ V$
$(iv)$ $D + 2e^- \rightarrow D^{2-} ; E^o = +0.68 \ V$

The reduction potential values are given below. Which is the strongest reducing agent? $Al^{3+}/Al = -1.67 \, V, Mg^{2+}/Mg = -2.34 \, V, Cu^{2+}/Cu = +0.34 \, V, I_2/2I^- = +0.53 \, V$

If the reduction potential is more,then

For the cell reaction,$2Ce^{4+} + Co \to 2Ce^{3+} + Co^{2+}$,$E^\circ_{cell}$ is $1.89 \ V$. If $E^\circ_{Co^{2+}/Co} = -0.28 \ V$,then $E^\circ_{Ce^{4+}/Ce^{3+}}$ is equal to: