题型:判断题 -Where is Miss Lee, do you know?-_____ she is in the library. She said she wanted to borrow some books.[ ]A. MaybeB. May beC. MayD. Must 查看答案
题型:判断题 交流接触器的栅片灭弧原理是由于触点上方的铁质栅片(),电弧上部磁通大都进入(),使电弧周围空气中的磁场分布形成(),将电弧拉入灭弧栅。电弧被栅片分割成若干短弧,使起弧电压()电源电压并产()效应,栅片又大量吸收电弧的(),所以电弧被熄灭。 查看答案