H3PO4的pKa1,pKa2,pKa3分別是2.12,7.20,12.40,欲用H3PO4和NaOH配制pH=7.20的緩沖溶液時(shí),應(yīng)使用H3PO4和NaOH的物質(zhì)的量之比為:()
A.1:2B.2:3C.3:2D.1:1