裂解使用的自保阀,在工作时,它的动力是()。
A.36V电
B.380V电
C.净化风
D.非净化风
参考答案:C
Jackie, you ________ hang all your clothes in the room like this![ ]
A. wouldn't
B. needn't
C. mustn't
D. oughtn't
法兰盘的平面应垂直于管子中心线,其倾斜度可以超过规定数值。