1 . There is nothing more i    1     to life than the sun. W    2     the sun, all living things on the earth would die. The sun is a star. In the sky there are t    3     of stars like the sun. They are as large as the sun and as h    4     as the sun. At night you can see many stars, but in the day you can only see one star—the sun.

The sun is much n    5     to us than any other star. That is w    6     it looks the biggest and brightest of all the stars. The distance (距离) of the sun from the earth is as m    7     as 150,000,000 kilometers. Most stars are thousands of light-years a    8     from the earth.

Do you know what a light-year is? N    9     in the world travels faster than light. It travels 300,000 kilometers per second. And one light-year is the distance that light can travel in one y    10    .