What is the Brønsted–Lowry conjugate base of ${{\text{H}}_{\text{2}}}{\text{PO}}_4^ -$?

A.     ${{\text{H}}_{\text{3}}}{\text{P}}{{\text{O}}_{\text{4}}}$

B.     ${\text{HPO}}_4^{2 - }$

C.     ${\text{PO}}_4^{3 - }$

D.     ${\text{H}}{{\text{O}}^ - }$

B