The standard reduction potential of some electrodes are, <br> ${E^ \circ }\left( {{{\rm{K}}^ + }/{\rm{K}}} \right) = - $ 2.9 V, <br> ${E^ \circ }\left( {{\rm{Z}}{{\rm{n}}^{2 + }}/{\rm{Zn}}} \right) = - 0.76{\rm{V}},{E^ \circ }\left( {{{\rm{H}}^ + }/{{\rm{H}}_2}} \right) = - 0.00{\rm{V}}$, <br> ${E^ \circ }\left( {{\rm{C}}{{\rm{u}}^{2 + }}/{\rm{Cu}}} \right) = + 0.34{\rm{V}}$ <br> The Strongest oxidant is :