下列说法正确的是[ ]

A．0.5 mol/L所有一元酸中氢离子浓度都是0.5mol/L

B．强酸溶液中氢离子浓度一定大于弱酸溶液中氧离子浓度

C．电解质溶液导电的原因是溶液中有自由移动的阴阳离子

D．熔融的电解质都能导电

— We _____ that you would fix the TV set this week.

— I'm sorry.I _____ to fix it this week,but I've been too busy.[      ]

A. had expected;had intended    

B. are expecting;had intended

C. expect;intend                

D. expected;intend