题目

—__________? —I have a sore back. A．What's the wrong       B．What's matter       C．What's trouble                D．What's wrong 答案：D在下列实际电路中各元件之间属于并联的有（　　）A．．教室里的各盏灯B．．电筒中的2节电池C．．家里电灯和开关D．学校的电铃和开关