【正文】
far enough away from the earth, we find there is no air. Maybe we can answer some questions now. What is the sky? Where is it? It is all round the world. The sky is space (宇宙空間 ). In space there is nothing, but only the sun, the moon, and all the stars. often think the sky is blue because_____. A. we think it is so B. we like this colour C. we don’t have other colours D. we don’t like other colours sky is ______. A. a star round it B. a big ball with air all C. full of dust D. space with the sun, the moon and the stars makes us thin k the sky is blue? A. Dust in the sky. B. Air and blue light. C. Our own feeling. D. Both A and B. can’t fly very high because ______. A. there’s too much air in the high place B. the high sky is full of dirty air C. there is no air in the high enough sky D. the sun is too hot writer of the passage ______. A. tells us something about the sky B. wants to tell us not to go to space C. once flew in the sky D. enjoys answering people’s questions Keys:一、 二、 one more time the word trying