It is polite in public piaces.a keeping your voice downb to keep your voice upc keeping your voice upd to keep your voice down

问题描述:

It is polite in public piaces.
a keeping your voice down
b to keep your voice up
c keeping your voice up
d to keep your voice down

It is polite _d to keep your voice down_ in public places.
公众地方小声说话是基本礼貌.