The higher oxidation states of transition elements are found to be in the combination with A and B, which are:

Because F and O are the most electronegative elements, the higher oxidation states of transition elements are found to be the combination with F and O. For example, Os has the highest oxidation state of +8 in ${\mathrm{OsO}}_4$. Similarly, Mn has the highest oxidation state (+7) in ${\mathrm{KMnO}}_4$.