下列关于肌紧张的描述，正确的是
A．由快速牵拉肌腱而引起B．感受器是肌梭C．人类以屈肌肌紧张为主要表现D．反射持久进行时易疲劳
参考答案：B
They all wanted to be teachers at that time, but _____ are teachers now. [ ]
A. none
B. none of them
C. no one
D. both
YJ27滤嘴接装机靠拢鼓轮左上方导纸板的作用是防纸片皱折及（）。
A.移位
B.翘边
C.弄脏
D.固定纸片
