一台30KW的电动机其输入的有功功率应该()。
A.等于30KW
B.大于30KW
C.小于30KW
D.不确定
参考答案:D
I _____ have been more than six years old when the accident happened.
[ ]
A. shouldn't
B. couldn't
C. mustn't
D. needn't
为使单销外槽轮机构的运动系数大于零,槽轮的径向槽数应大于()。
A.2
B.4
C.3
D.5