【简答题】下列有关发电机定子的描述中,正确的是( )。 A. 定子有三相绕组,工作时产生三相交流感应电动势 B. 定子产生旋转磁场,由磁轭及爪型磁极组成 C. 定子位于发电机最中心位置 D. 定子由发动机驱动,定子轴上有滑环
【单选题】若全集U={1,2,3,4,5},集合A={1,4},集合B={3,4},则集合{2,5}等于( )
【单选题】The story _____in China. A. was taken place B. was happened C. took place D. has been taken place
【单选题】在Excel2003中,把建立的文件称为______。
【简答题】Paraphrase the following sentences. (Explain the following sentences in your own words and try to bring out the implied meanings) 1. Were elevated 23 feet (Para. 3) 2. The place has been here since 19...