It’s better your voice down in public places.A. keepingB. to keepC. keepsD. keep

问题补充：

It’s better your voice down in public places.

A. keeping

B. to keep

C. keeps

D. keep

答案：

A. keeping

(答案→)B. to keep

C. keeps

D. keep

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。结合语境可知选B。