一般来说,三相异步电动机越大,效率越高,转差率越小。()
参考答案:对
一个数是7,另一个数是5,积是______,再加上46,和是______.
(2013·江苏南通市二模)We ________ have hurried all the way to the airport — the flight was called off because of the foggy weather.
A.mustn't
B.couldn't
C.needn't
D.wouldn't