什么是直流电、交流电？
参考答案：
直流电指电流方向一定且大小不变的电流；交流电指方向和大小随时间变化的电流。
( )负责施工现场标牌的保护工作。
A．建设单位
B．设计单位
C．施工单位
D．管理者代表
His suggestion was that we early tomorrow moming. [ ]
A. are to leave
B. leave
C. were to leave
D. would leave
