explain how the answer is correct

6. Consider the adjacent titration curve of phosphoric acid (H3PO4). What species will be present when 0.25 equivalents of OHhas been added? A) essentially all PO43 G) 75:25H2PO4and HPO42 (B) 75:25H3PO4 to H2PO4 H) 25:75H2PO4to HPO42 C) 25:75H3PO4 and H2PO4 1) essentially all H2PO4 D) 50:50H3PO4 to H2PO4 J) 50:50HPO42 and PO43 E) essentially all HPO42 K) essentially all H3PO4 F) 50:50H2PO4to HPO42 L) none of the above