We want to explore and try to better understand the world in which we live. Space exploration is one of the ways.Through the exploration of space, we can begin to unravel the mysteries of our universe, and to better know our living environment.
Space exploration provides us with knowledge about the beginning of our solar system, our own planet and ourselves. It also helps answer the questions that have puzzled us for many years. Solar system exploration is important because it is good for us.
Space technology has become an important part of our daily lives. Some technology uses satellites to communicate. Satellites are also used to examine the changes in the Earth's climate and seas, for weather report and for military. We also use satellites in food production. Because of the use of space technology in crops, fewer and fewer people will suffer hunger.
The space program provides a chance for nations to work together. The cooperation(合作) promotes peace and understanding between governments and their people. Many governments have taken part in the space technology, including the United States, Russia, Japan, the European nations and India. In the near future, other nations will take part in it. In fact, the United States remains the leader in new space technology.
阅读下面短文，按照句子结构的语法性和上下文连贯的要求，在空格处填入一个适当的词或者使用括号中词语的正确形式填空。
Over millions of years ago, there were deserts. Now about one fifth of the Earth's surface (be) deserts. The size of the world's deserts is always (change). Deserts can be hot or cold. The Australian Desert is a hot desert, while the Gobi Desert in Mongolia is an example of a cold desert. Deserts are dry areas less than 50 cm of rain falls each year. The Sahara Desert in Africa receives less than 1.5 cm a year. rain doesn't fall very often in deserts, sometimes even for years, there can be heavy rain (sudden). Because they are dry, deserts have wide changes in temperature each day. When the sun (go) up, it is very hot. At night, the heat (receive) by the ground during the day (quick) disappears(消失), and then it becomes very cold. Because the change, living in the desert is very difficult. Man can make deserts, but they can also stop them from getting larger and larger. Planting trees can prevent the sand from (spread).
