When you see some waste paper on the ground, you should _______ and put it in the trash bin.

A．give it away

B．pick it up

C．turn it on

D．put it out

随着工业的发展，排放到空气中的__________ 和__________ 对空气造成了污染，“温室效应”“酸雨”“臭氧层空洞”等都是空气污染引发的环境问题。