题目内容：

根据句意首字母或汉语提示完成单词。

1.L____ travels much faster than sound.

2.Some spacecrafts have gone b____（在……之外）the solar system.

3.Scientists have discovered many other planets in the u ____.

4.The earth is a p ____ and we live on it.

5.The Mars is a _____ (行星)in the solar system.

6. You should      (交流) with your friends more often.

7.How many      (组) are there in your team?

8.We should protect our      (环境) well.