Drivers are warnedwhen they are tired.A. to driveB. not driveC. not to driveD. not driving

问题补充：

Drivers are warnedwhen they are tired.

A. to drive

B. not drive

C. not to drive

D. not driving

答案：

A. to drive

B. not drive

(答案→)C. not to drive

D. not driving

解析：本题考查动词用法。warn sb not to do sth，表示警告某人不要做某事。句意：司机被警告当他们劳累的时候不要开车。