问题补充：
The policeman warned the driver too fast. It was very dangerous.
A. to drive
B. not to drive
C. driving
D. not driving
答案：
A. to drive
(答案→)B. not to drive
C. driving
D. not driving
解析：根据下文,这非常危险.可知前文意思为:警察警告这个司机不要开得太快.不定式不宾语补足语表示具体的将要进行的动作,其否定式,是在不定式符号to的前面加not,warn后接带to的不定式,故选B.
