question_answer

Three reactions involving \[{{\text{H}}_{\text{2}}}\text{PO}_{\text{4}}^{\text{-}}\] are given below \[\text{I}\text{.}\] \[{{\text{H}}_{\text{3}}}\text{P}{{\text{O}}_{\text{4}}}\text{+}{{\text{H}}_{\text{2}}}\text{O}\to {{\text{H}}_{\text{3}}}{{\text{O}}^{\text{+}}}\text{+}{{\text{H}}_{\text{2}}}\text{PO}_{\text{4}}^{\text{-}}\] \[\text{II}\text{. }{{\text{H}}_{2}}\text{PO}_{4}^{-}\text{+}{{\text{H}}_{\text{2}}}\text{O}\to \text{HPO}_{4}^{2-}\text{+}{{\text{H}}_{3}}{{\text{O}}^{+}}\] \[\text{III}\text{. }{{\text{H}}_{\text{2}}}\text{PO}_{\text{4}}^{\text{-}}\text{+O}{{\text{H}}^{\text{-}}}\to {{\text{H}}_{\text{3}}}\text{P}{{\text{O}}_{\text{4}}}\text{+}{{\text{O}}^{\text{2-}}}\] In which of the above does H^O^ act as an acid?

A) II only                   

B) I and II  

C) III only                                 

D) l only