题目

氢氰酸(HCN)的下列性质中,可以证明它是弱电解质的是 A．HCN易溶于水 B．1mol/L氢氰酸溶液的pH约为3 C．10 mL1mol/LHCN恰好与10 mL 1mol/L NaOH溶液完全反应 D．HCN溶液的导电性比盐酸溶液的弱 答案：B ____ three times in a row, the boxer decided to give up fighting.          A. Having defeated  B. To have defeated  C. Having been defeated  D. To have been defeated