Air is all around us. It is around us as we walk and play. From the time we were born air is around us on every side. When we sit down, it is around us. When we go to bed, air is also around us. We live in air. We can live {#blank#}1{#/blank#} food or water for a few days, but we can't live for more than a few {#blank#}2{#/blank#} (minute) without air. We take in air.

    When we are working {#blank#}3{#/blank#} running, we need more air. When we are {#blank#}4{#/blank#} (sleep), we need less air .We live in air, {#blank#}5{#/blank#} we can't see it. We can only feel it when it {#blank#}6{#/blank#} (move). Moving air is called {#blank#}7{#/blank#} (windy). How can we make air move? Here {#blank#}8{#/blank#} (be) one way. Hold {#blank#}9{#/blank#} open book in front of your face, close it {#blank#}10{#/blank#} (quick). What can you feel? What you feel is air.

    More than millions of years ago, there were deserts. Now about one fifth of the Earth's surface {#blank#}1{#/blank#} (be) deserts. The size of the world's deserts keeps {#blank#}2{#/blank#} (change). Deserts can be hot or cold. The Australian Desert is a hot desert, while the Gobi Desert is a cold desert. A desert is a very dry land and there is hardly any rain. The Sahara Desert in Africa receives less than 1.5 cm a year. {#blank#}3{#/blank#} it doesn't rain very often in deserts, sometimes even for years, there can be heavy rain suddenly. Because they are dry, deserts have wide changes in temperature each day. When the Sun goes up, it is very hot, even hot enough {#blank#}4{#/blank#} (fry) an egg on the ground. At night, the heat that {#blank#}5{#/blank#} (receive) by the ground during the day disappears {#blank#}6{#/blank#} (quick), and then it gets {#blank#}7{#/blank#} cold that water would turn into ice. Because {#blank#}8{#/blank#} the change, living in the desert is very difficult. Man can make deserts, but man can also stop {#blank#}9{#/blank#} (they) from getting larger and larger. Planting trees can prevent the sand from {#blank#}10{#/blank#} (spread).

    Many people like animals and take them as their pets, so pet hospitals are usually very busy. Kind persons {#blank#}1{#/blank#} love animals are needed to help in busy animal hospitals. Vets (兽医) will teach them {#blank#}2{#/blank#} to take care of the animals.

    Scientists think that pets will {#blank#}3{#/blank#} (probable) be much smaller {#blank#}4{#/blank#} people in the future will live in much smaller space. Scientists are now working on making very small farm animals, and the same thing might be done to make small cats and dogs.

    It {#blank#}5{#/blank#} (be) said that some day you might own a panther (豹) as a pet. Some scientists believe that they might have to start turning wild animals into pets, since this might be the only way to save them from {#blank#}6{#/blank#} (die) out.

    What about taking a robot as a pet? This may sound strange, {#blank#}7{#/blank#} it could become true. Robot dogs have been made {#blank#}8{#/blank#} (sell). They are like real dogs. These pets might become more and more popular in the future.

    Lots of people miss their pets when they are {#blank#}9{#/blank#} holiday. One hotel in Minnesota has solved this problem. It lends cats to their guests. Many expels believe more and more people will like this idea. It is very possible that in the future you will be able to order a pet, as well as room service, at {#blank#}10{#/blank#} hotel.