Since the beginning of time, man 1 many interesting things．Some of these inventions, 2 numbers, the alphabet and the radio, have certainly changed history．
One of the most important 3 has been the computer since 1946．It changed all our lives．
The first computer 4 at Harvard University in 1944．It was as large as a room and quite difficult and slow to operate．But since the invention of silicon(硅)chip, computers have become smaller, easier 5 , and faster to operate．Some computers are as 6 as television sets．Simple computers can be made smaller than a book．And computers are getting smaller all the time．
There are several reasons why computer is useful to us．First, it can store(储存)very, very large amounts of information in its memory chips． 7 , the computer can operate very quickly． 8 times faster than humans and it will never feel tired．Third, modern computer can be built into other kinds of machines, like radios, cars, and planes．They can do a lot of work for us．
Soon, almost everyone, either at home 9 at work, will use some kind of computer．The lives of all of us 10 by this invention．
The weather in our town today is different from that many years ago．It was too hot at the time．Now it becomes 1 because all the mountains around our town 2 trees．There is no more sand on the surface of the earth 3 these new trees．At the beginning of this century, sand was 4 here． 5 we couldn't 6 any plants in this poor land．In 1952, a number of young people came to live here．They wanted 7 this poor land with their hands．They worked hard to plant trees to stop earth 8 sending away．After many years of hard work, a beautiful new town 9 on the poor land．Now, people on this town still go on planting more trees all the time．They want to keep it much more beautiful later 10 ．