当电动机带动叶轮转动时，迫使叶轮中叶片之间的（）跟着旋转，因而产生了离心力。
参考答案：气体
画出下列各图中通电直导线A受到的安培力的方向（或做必要文字说明）．
Why not stay at home _____ the road is so slippery after the heavy snow? [ ]
A. since that
C. then that
B. now that
D. after that
