哪种病不属于运动神经元病（）
A.肌萎缩侧索硬化
B.进行性脊肌萎缩
C.原发性侧索硬化
D.进行性延髓麻痹
E.脊肌萎缩症
参考答案：E
7.Although the causes of cancer ____， we do not yet have any practical way to prevent it.
A．are being uncovered
B．have been uncovering
C．are uncovering
D．have uncovered
A．mgtgθ
B．mgsinθ
C．μmg
D．μmg
mgtgθ
mgsinθ