Greater the number of valence electrons, more will be the number of oxidation states exhibited by the element. Option (a) : 3d54s1, can show a maximum of 6 oxidation states Option (b) : 3d54s2, can show a maximum of 7 oxidation states. Option (c) : 3d24s2 can show a maximum of 4 oxidation states. Option (d) : 3d34s2 can show a maximum of 5 oxidation states.