对于长期空载运行的变压器应切断电源停止运行。
参考答案：对
—Does Bob's sister usually get home at four?
—_____. [ ]
A. Yes, she is
B. No, she aren't
C. Yes, she does
D. No, he doesn't
随着树脂含量的增加，沥青的塑性（）
A.增大
B.减小
C.不变
D.增大或不变
