阅读理解。 We know the sun, the earth and the moon are in the universe. We see the sun in the daytime and the moon in the night. The sun is much bigger than the earth, and the earth is bigger than the moon. So the sun is the biggest and the moon is the smallest. The earth goes round the sun day and night. It goes at 30 kilometers a second. The moon is our satellite (卫星). It is also our neighbor. It goes round the earth all the time. The moon goes at 8 kilometers a second. The moon can't give out light or heat itself, and nothing can live on it. Men live on the earth. It is going round itself all the time. The earth gives us lives, food, water and so on. We must get on well with it. 根据短文内容，补全下面句子（每空一词）。 1. The sun is the b______of the three. 2. The e______ is bigger than the moon, but s______than the sun. 3. The m______ goes round the earth. 4. We can see the moon in the n______. 5. Men must get on w______ with the earth