Three things are necessary for us to keep alive. What are they? They are air, water and food. We eat food twice 46 three times a day. We drink water several times a day. We breathe air day and 47 . If a man does not eat 48 food and does not drink anything,he can live for about three days. But if he does not breathe, he can keep alive for only about three minutes. 49 we can see that breathing is more important 50 drinking, and drinking is more important than eating. We 51 live if there is no air or water or food. For us, food is very important, water is more important, and air is the 52 important. Why? Because we can only live for about three minutes 53 air. Three minutes— 54 a short time it is! Food and water are less important than air, but we can’t be short of them, 55 .