从所给的四个选项中，选择最合适的一个填入问号处，使之呈现一定的规律性（）
A．
B．
C．
D．
参考答案：C
— What were you doing at this time yesterday?
— We _____ in the classroom. [ ]
A. read
B. were reading
C. are reading
D. was reading
20世纪70年代呼叫中心主要集中行业不包括？（）
A.民航业
B.银行业
C.旅游业
D.工业
