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 一The smoke       factories makes the air dirty．

  Air has no c{#blank#}1{#/blank#}, t{#blank#}2{#/blank#}, s{#blank#}3{#/blank#}or shape. We can't see it or smell it, but we can f{#blank#}4{#/blank#}it. Air is e{#blank#}5{#/blank#}around us. When air moves, it becomes w{#blank#}6{#/blank#}. The air moves quickly and the wind blows s{#blank#}7{#/blank#}. The air moves s{#blank#}8{#/blank#}and the wind blows g{#blank#}9{#/blank#}. Air is i{#blank#}10{#/blank#}to all of us. Without air, we will all d{#blank#}11{#/blank#}. Dirty air is b{#blank#}12{#/blank#}for our health. So let's try our best to k{#blank#}13{#/blank#}the air clean.

    Air，I can't see it．I can't touch it．But I 1.can live without it．This is air．Air 2.are very important．It is all around US when we walk and play．It is all around US when we sit down3. or sleep．We need 4.airs ．

All living things5. needs air．We can live without food or water for a few days，but we cannot live without air for even a few minutes．When we 6.are work or run．we need more air．When we are asleep，we need less air．