题目

如图所示，当S1、S2断开时，能亮的灯是， 它们是串联的；当S1、S2闭合时，能亮的灯是， 它们是并联的；当S1闭合，S2断开时，能亮的灯是 答案：【1】L1、L3【2】L2L3【3】L3听对话，完成下列各小 题。【1】What happened to Henry yesterday?A. He was ill.B. He was lost.C. He took a wrong bus.【2】Which bus will Jane take at last?A. No.7.B. No.13C. No.21.