—You ______ turn on the light. It's bright enough here.    

—OK. I will turn it off right now.   [ ]

A. mustn't

B. can't

C. needn't

D. won't

汽油机主要由（）组成

A.曲柄连杆机构、配气机构

B.燃料供给系统、点火系统

C.润滑系统

D.冷却系统

E.启动装置