What Is the Conjugate Acid of HBO₃^{2 -}

What is the conjugate acid of HBO₃^{2 -} ?

A) H₃BO₃
B) H₂BO₃^{1 -}
C) H₂BO₃^{3 -}
D) BO₃^{3 -}
E) BO₃^{1 -}