A:I'm going to climb mountains.
B:I climbed mountains.
C:I am climbing mountains.
利用两个相同的单刀双掷开关A和B,小明设计了一个电路,使电动机通过控制开关的操作,既能正转,也能反转(说明:图中开关A既可以与“1”触点接通,也可以与触点接通).在虚线框内把未完成的电路补充完整.
— She didn't finish my homework _____ my father came back.
— So you went to bed too late.
(电力的广泛应用改了人类的生产生活方式,以电力为核心的技术革命是( )