Which region(s) of the periodic table contains elements that can adopt both positive and negative oxidation numbers?

The region(s) of the periodic table which contains elements that can adopt both positive and negative oxidation numbers would be the nonmetal region. As you look at the periodic table, you can see that some elements on the right side of the table would have two oxidation states written one positive and other a negative sign. 

Ithink the answer is a or d.