A: Did you go ____ (shop) yesterday?
B:No, I didn't. I ____ (wash) my clothes and ____ (clean) my room.
图所示是某同学连接的电铃电路.当开关闭合后,电路被接通,电磁铁____ ,衔铁____ ,使小锤敲击铃碗发出声音,同时衔铁与螺钉脱离接触,电路____ ,电磁铁____ ,小锤在弹簧片的作用下又恢复到使电路接通的状态.
施莱登和施旺共同提出