Better all the lights are turned off before you leave the classroom．A. to be sureB. to ma

问题补充：

Better all the lights are turned off before you leave the classroom．

A. to be sure

B. to make sure

C. be sure

D. make sure

答案：

A. to be sure

B. to make sure

C. be sure

(答案→)D. make sure

解析：Better = Had better, 后接动词原形。