Identify the reaction from following having top position in EMF series (Std. red. potential) according to their electrode potential at 298 K.

Au3++3e−→Au(s)    E∘=1.40VFe2++2e−→Fe(s)    E∘=−0.44VMg2++2e−→Mg(s)    E∘=−2.36VK++1e−→K(s)    E∘=−2.93VAs per electrochemical series, Au3+ occupies the top position.