Use the following standard electrode data to answer this question. $$Ag \rightarrow Ag^+ + e^-$$ has $$E^0 = -0.80$$ V, $$Cr^{3+} + 3e^- \rightarrow Cr$$ has $$E^0 = -0.74$$ V, $$Zn^{2+} + 2e^- \rightarrow Zn$$ has $$E^0 = -0.76$$ V, $$I_2 (s) + 2e^- \rightarrow 2I^-$$ has $$E^0 = 0.54$$ V, $$Co^{2+} + 2e^- \rightarrow Co$$ has $$E^0 = -0.28$$ V and $$Ni^{2+} + 2e^- \rightarrow Ni$$ has $$E^0 = -0.26$$ V. The best reducing agent among the following is