+3 oxidation state is most common in

Let us consider the stable oxidation states for each given element, 8 2 2+ 8 6 2 3+ 5 10 2 2+ 10 10 1 + 10 Ni [Ar]3d 4s ,Ni [Ar]3d Fe [Ar]3d 4s ,Fe [Ar]3d Zn [Ar]3d 4s ,Zn [Ar]3d Cu [Ar]3d 4s ,Cu [Ar]3d → → → → → → → → Only Fe can achieve the stable half-filled configuration with +3 oxidation state. Therefore, option B is correct.