在图中,将实物图连接成串联,要求:导线不能交叉.并画出电路图.
先串联干电池,然后按电流流向法,从电源的正极出发,依次串联开关、灯泡L2、灯泡L1回到负极,实物图和电路图如下:
矿井必须坚持()、()的探放水原则。
He _____ home once a week, but after entering middle school, he _____ home once a month. [ ]
A. was used to go, was used to go
B. used to go, was used to go
C. was used to go, used to
D. used to go, was used to going