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Across 3. the air from the out side which air especially clean air 5. a poisonous substance, especially one that is produced by bacteria and causes a particular disease 8. the state that being dangerously dirty. 9. having the colour which on the grass or leaves

Down 1. the living that releasing oxygen and absorbing carbon dioxide. 2. Gas that tree use to photosynthesize. 4. A gas that people use to breathe. 6. everything in the physical world that is not controlled by humans, such as wild plants and animals, earth and rocks, and the weather 7. a medical condition in which you become ill or in which your skin red and painful. 8. Coarse particles that have a diameter of 2.5 micrometers