Oxygen - The gas ,which is present the most in air, Acid rain - Mixture of acidic gases with rain water, Greenhouse effect - Phenomenon which helps the earth to maintain its surface temperature, Water vapour - Gaseous form of water, Photosynthesis - Process of making food by plants, Nitrogen - The gas ,present in air is essential for the growth of plants, Smoke - An air pollutant, which exists in solid form, Polluted air - The air having impurities , Global warming - Additional increase in the average temperature of earth, CNG - Cleaner fuel for running vehicles,

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