Phosphoric acid (h3po4) has three acid dissociation constants ( ka). the first dissociation constant has the greatest value, and it applies to the reaction described by which equation?

Missing question:
A. H3PO4 (aq)<--> H+ (aq) + H2PO4- (aq).
B. H2PO4- (aq)<--> H+ (aq) + H2PO4-^2- (aq).
C. H3PO4 (aq)<--> 2H+ (aq) + HPO4^2-(aq).
D. HPO4^2- (aq)<--> H+ (aq) + PO4^3- (aq).
Answer is: A. H3PO4 (aq)<--> H+ (aq) + H2PO4- (aq).
The first dissociation constant :Ka₁ = [H+]·[H₂PO₄⁻] / [H₃PO₄].
In first dissociation phosphoric acid lost one proton (hydrogen ion).