A．c (B^2? ) + c (HB^? ) + c (H₂B) = 0.1 mol/L

B．c (Na⁺ ) + c (OH^? ) = c (H⁺) + c (HB^? )

C．c (Na⁺ ) + c (H⁺ ) = c (OH ^? ) + c (HB^? ) + 2c (B^{2 ?} )

D．c (Na⁺ ) = 2c (B ^2? ) + 2c (HB^? )