We know the earth is a planet．There are seven other planets，and they go  1 the sun together．The eight planets and the sun are2 the solar system．The first planet，3   the sun，is Mercury(水星)．It is 58 miIlion  4  from the sun．Venus(金星)is the second planetfrom the sun，and  5 planet，the earth，is the third．It is from the sun,and 55  planet,the earth,is the third.It is 2,650 million kilometres from the sun．

    Jupiter(木星)，Saturn(土星)，Neptune(海王星)and Uranus(天王星)are all 6 than the earth，7 Venus，Mars and Mercury are smaller than the earth．

    Animals，trees and humans can only 8  on the earth，because the other planets in our solar system don't  9  air or water．Do any  10planets in   solar systems have life?We don't know about it．

    Man has    1 four kinds of satellites. The first kind of satellites studies the   2    of the earth. They are used to make maps. They also help countries to see    3   they can find oil or gold.

    The second kind of satellites is used to guide   4   and planes. A ship or a plane can        5    a message to the satellite, and the satellite can find out where it is. The third kind of satellites studies the  6    . These satellites watch clouds and strong winds   7   across the earth. They warn countries to make preparations when very   8 weather is coming. They take photos of the earth from miles above it and send the photos to weather   9   on the ground.   The last kind is used for    10  .Telephone calls 11 countries can be sent by these satellites. Some can carry hundreds of 12   at one time. The call is sent to the satellite and then the satellite send it to the station in the country  13  is being phoned. These satellites also carry    14 , they can send about eight programs  15   .

    It's March 12^th. Li Li and Lin Tao are digging on a hill nor far from their school. In China, people across the country plant trees1on this day.

    The idea of planting trees was first put forward in 1911 by Sun Zhongshan, the great2 in China's history. He said more trees were needed as a3against flood(洪水)and drought. In 1915, April 5^th was named as Tree Planting Day. Then, in 1979, the day4to March 12^th, to 5the date on which Sun Zhongshan died.

    "Everyone has heard of the Great Wall of China," says Li Li. "But have you heard of the Green Wall of China? That's the biggest tree planting 6 of all. "The Gobi Desert in the north of China was 7every year. So in 1978, a tree planting project was started to 8 Gobi spreading. The government and local farmers have been planting millions of trees to build a great green "wall" along the edge of the desert.

    "Tree planting has become a tradition in China now," says Lin Tao. "Almost everyone does it on March 12th. Many people also plant a tree on a 9 day. My parents planted a tree when started school. And my cousin planted 10 on his wedding (婚礼) day. We do it for the environment and for ourselves."

    Arctic fox (北极狐) is a kind of small fox that lives in the Arctic. It grows about 50 centimeters long, not including its tail, 30 centimeters tall and 1 from 3 to 7 kilos.

    The Arctic foxes are white or blue 2 color. The white ones are white in winter,3 gray-brown in summer. The blue ones are blue-gray all year round. The Arctic foxes have long thick hair 4 is called fur. And the long fur covers their whole bodies, including both their cat eyes and rabbit feet, to keep them 5in the low temperature in the Arctic.

    The Arctic foxes feed mainly on birds, birds' eggs and other small animals. Teamwork is the way they look for food, and they don't like to do that 6.

    Baby Arctic foxes are very lovely. They don't.7their eyes until a week after their birth. For the first half of the year, their parents offer them food. They begin to 8food on their own when they are about six months old. The next year they can live alone.

    Today,9the Arctic foxes is becoming smaller and smaller, because people kill them for their 10to make beautiful coats for money. Something must be done to protect the Arctic foxes.