When you are sleeping, you had better all the windows closed.
A. don’t keep
B. not keep
C. not to keep
D. not keeping
网友回答
A. don’t keep
(答案→)B. not keep
C. not to keep
D. not keeping
解析：固定结构had better表示最好做某事，后跟动词原形；其否定形式在动词原形的前面加not即可。结合语境可知是考查had better的否定结构，故选B。