优质空气利于身心健康。均会造成空气污染的一组物质是( ) A.O2和N2 B.水蒸气和O2 C.SO2和NO2 D.水蒸气和N2 答案:C3.At night,plants _________carbon dioxide and at the same time _________oxygen.So,we may put some in our bedrooms to purify the air.( )A.take in,give outB.take up,give offC.take in,give inD.take off,give up