Air is always around us. It is around us when we walk and play. From the time we are born, air is around us. When we sit down, it is around us. When we go to bed, air is also around us. We live in air. All the animals and plants need air. Living things can't live without air. We can live without food or water for a few days, but we can not live for more than a few minutes without air. We breathe in air. When we are walking or running, we need more air. When we are asleep, we need less air. We live in air, but we can't see it. We can only feel it. We can feel it when it is moving. Moving air is called wind. How can we make air move? Here is one way. Hold and open a book in you hand in front of your face. Close it quickly! What you feel is the air. We need   _   air when we are asleep.
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