活塞式压缩机按（）分为立式压缩机、卧式压缩机、角式压缩机、对称平衡式压缩机。
A.活塞的动作
B.工作的压力
C.气缸排列
D.输送的气量
参考答案：C
——Your friend Alice looks down today. What is up?
——Well, ________ happened to her was her own fault!
A．wherever
B．However
C．whatever
D．No matter what
当一带正电的物体与带电的验电器的金属球接触后，金属箔张角逐渐减小合上后又逐渐增大，则验电器原来带__________电．
