$(i)\, A3^-\rightarrow A^{2-} + e; E° = 1.5 \,V$
$(ii) \,B^{+}+ e \rightarrow B; E° = 0.5 \,V$
$(iii)\, C^{2+} + e \rightarrow C^{+}; E°= 0.5\, V$
$(iv)\, D \rightarrow D^{2+}+ 2e; E° = -1.15\, V$
$Pt | H_2\,(g) | H^{+}_{(aq)} (10^{-8}\, M) | | H^{+}_{(aq)} (0.001\,M) | H_2\,(g) | Pt$