The UN Climate Change Conference in Copenhagen was held in a tense ______ due to lack of deep understanding.

A．atmosphere

B．state

C．situation

D．phenomenon

每年6月5日是世界环境保护日。环境保护是我国的一项基本国策，空气的质量越来越受到人们的关注。下列各组气体都属于空气的污染物的是 (        )

A．CO₂、N₂

B．NO₂、O₂

C．CO、CO₂

D．SO₂、NO₂