1) Photosynthesis produces a) oxygen b) carbon dioxide c) hydrogen 2) Photosynthesis needs a) oxygen b) carbon dioxide c) hydrogen 3) Our lungs draw in a) smoke b) carbon dioxide c) oxygen 4) Our lungs expel a) oxygen b) carbon dioxide c) hydrogen 5) Burning requires a) water vapour b) oxygen c) dust 6) Harmful substances found in the air a) germs b) water vapor c) nitrogen

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