掘进机开机时发出报警信号。开启抑尘装置，并打开各转载点（）装置。
A.喷雾
B.烟雾报警
C.压风
D.运行
参考答案：A
In the last few years thousands of films _____ all over the world. [ ]
A. have produced
B. have been produced
C. are producing
D. are being produced
电动机的绝缘等级分为（）五级。
