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
