串联电路的特点是总电压等于（）.
参考答案：各电阻上的电压降之和
The play had already been on for quite some time when we _____ at the New Theatre. [ ]
A. have arrived
B. arrived
C. had arrived
D. arrive
可作为栓剂硬化剂的是（）
A．巴西棕榈蜡
B．尿素
C．甘油明胶
D．叔丁基羟基茴香醚
E．羟苯乙酯
