石膏类模型材料的凝固原理是 A．CaSO4·1/2H2O→CaS04·H2O B．C

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other, move, enough, find ,desert, make, use another, friend , carry , trouble, friendly

You may think there is nothing but sand in the desert of the world, but it is not true. In the desert we can   76   stones. We can see hills, too. There is a little rain in the   77  , but it is not   78  for most plants.
　　The animals are   79  to the desert people in many ways. The desert people eat the meat and drink the milk of the animals. They use their skins to    80  shoes, water bags and even tents(帐篷). They use the camels(骆驼) for   81  things.
The people of the desert have to keep    82  from places to place. They must always look for grass or desert plants for their animals. They usually live in the tents. When there is mo more food for their animals, they take down their tents, put them on the camels and move to    83  place. The desert people are very   84 . No man in the desert would ever refuse to help the people in   85  and give them food and water