Four successive members of the first row transition elements are listed with atomic numbers. Which one of them is expected to have the highest $E^0_{M^{3+}/M^{2+}}$ value ?

Question

( A ) $Mn ( Z = 25)$
( B ) $Fe ( Z = 26)$
( C ) $Co ( Z = 27)$
( D ) $Co ( Z = 24)$