意向性震颤是指（）

A.静止时震颤表现明显，而在运动时减轻，睡眠时消失

B.震颤在休息时消失，动作时发生，愈近目的物愈明显

C.触摸肌肉，坚实感，伸屈肢体时阻力增加

D.两组拮抗肌交替收缩引起的不自主动作

E.骨骼肌受到外力牵拉时产生收缩反应

— The radio is too noisy and there is nothing interesting on it. Why don't you ____?

— All right. I'll do that. [      ]

A. turn it on                        

B. turn it off

C. turn it back                      

D. turn it up