Which of the following consitute a set of amphoteric species?
(a). `H_(2)O,H_(2)PO_(3)^(Theta), HPO_(4)^(2-)`
(b). `HC_(2)O_(4)^(Theta),H_(2)PO_(4)^(Theta),SO_(4)^(2-)`
(c). `H_(2)O,HPO_(4)^(2-),H_(2)PO_(2)^(Theta)`
(d). `H_(3)O^(o+),H_(2)PO_(4)^(Theta),HCO_(3)^(Theta)`