什么叫振动？
参考答案：
由于风机叶轮不平衡，风机结构的刚度和旋转轴的同心度等都会使风机产生振动。
根性感觉障碍特点（）
A.呈手套、袜子样
B.有牵涉性疼痛
C.有扩散性疼痛
D.有末梢营养障碍
E.受损范围呈节段性分布
–Do you think most of the people in Beijing can talk with foreigners in English?
-- Yes, I think so. ________the young ________the old are learning to speak English.
A．Either ; or
B．Neither ; nor
C．Not only ; but also
D．not ; but
