Mary went to the box office at lunch time, but all the tickets ____ out. [ ]

A. would sell

B. had sold

C. have sold

D. was selling

为了除去氯化钠溶液中含有的少量硫酸镁杂质，应加入的一组试剂是[ ]

A．氢氧化钾溶液、硝酸钡溶液

B．氯化钡溶液、硝酸银溶液

C．氯化钡溶液、氢氧化钠溶液

D．硝酸钡溶液、硝酸银溶液