煤气爆炸需三个条件，哪一个不属于煤气爆炸的条件（）。
A.煤气浓度在爆炸限度范围内
B.含煤气的混合气体
C.高压
D.存在点火源
参考答案：C
用线条代替导线，将图中的电器元件连成电路．要求：
（1）开关S1只控制电灯L1；开关S2只控制电灯L2；共用一个电池组．
（2）在右面虚线框中画出对应的电路图．
Not only ________ their own ideas on the matter,but ________ theirs .
A．do the teacher have, do the students have
B．the teacher have, the students have
C．he teacher have,do the students have
D．do the teacher have, the students have
