Which components are used to make the standard hydrogen electrode?

A.     ${{\text{H}}_{\text{2}}}{\text{(g), }}{{\text{H}}^ + }{\text{(aq), Pt(s)}}$

B.     ${{\text{H}}_{\text{2}}}{\text{(g), }}{{\text{H}}^ + }{\text{(aq), Ni(s)}}$

C.     ${{\text{H}}_{\text{2}}}{\text{(g), H}}{{\text{O}}^ - }{\text{(aq), Pt(s)}}$

D.     ${{\text{H}}_{\text{2}}}{\text{(g), H}}{{\text{O}}^ - }{\text{(aq), Ni(s)}}$

A