架空线路的杆、塔上应涂写列标志，（）、引入杆应有相序标志。
A、开关杆
B、分歧杆
C、换位杆
D、转角杆
参考答案：A, B, C
—_________ model plane is this?
—I think it’s Jim’s. Look, his name is on it.
A．Who
B．What
C．Whose
D．Where
A．电源
B．开关
C．电磁铁
D．输电导线
