在旋风分离器中，内层的气流形成（）运动。
A、自下而上的直线
B、自上而下的直线
C、自下而上的螺旋
D、自上而下的螺旋
参考答案：C
—How was your holiday?
—It couldn’t have been ．I just stayed in the hotel because it was raining most of the time．
A．boring
B．more boring
C．most boring
D．1ess boring
什么叫操作电源？
