《消费者权益保护法》规定经营者有（）义务。
A、８项
B、9项
C、10项
D、11项
参考答案：C
A．石英玻璃
B．光学玻璃
C．陶瓷
D．地壳和半导体材料
What do you mean by saying there are only ten tickets? There _____ be twelve. [ ]
A. could
B. should
C. would
D. can
