电机绕组线圈的两个边所跨的距离称为（）。
A、极距；
B、节距；
C、槽距
参考答案：B
The leaders of the company are having a meeting to discuss where the new office building __.
A．should situate
B．should be situated
C．should be lied
D．was located
已知f（x）=xa，若f′（-1）=-4，则a的值等于[ ]
A.4
B.-4
C.5
D.-5
