1 . 阅读下列短文，根据短文内容填空。在未给提示词的空白处仅填写1个适当的单词，在给出提示词的空白处用括号内所给词的正确形式填空。
The earth, the planet on 1 we are living, is the third planet from the sun. It came from the shrinking (收缩) of a vast cloud of dust and gas in outer space. Many scientist believe that the earth, as well as the sun and the other planets in our solar system, 2 (form) at least five billion years ago. The earth is slightly flattened at the North and South Poles, 3 it would look like a perfect ball if you were far out in space.
