It was __________she was injured in the accident _______ she didn’t come to the party yesterday.

A.as; which    B. because; that    C since; why     D. for; how

电刷和滑环在滑动接触时，电刷下面的气流有抬起电刷的趋势，这种现象称为（）。

A.气垫现象；

B.悬浮现象；

C.离心现象；

D.电磁现象。