8. Mike found a (挑战性的) job as a computer programmer.

7. He made such (快的) progress that his parents were very glad

6. You must wear a (头盔) if you want to get into the building.

5. This kind of bike is (专门地) designed for disabled people.

4.(重力) will be a problem for the settlers on Mars.

3. There are eight (行星) in the solar system.

2. The bus was so (拥挤的) that I had to stand all the way.

19. 八分之三的……20. 在网上学校学习  

17. 载大量的乘客去火星18. 没有水、氧气或食物

15. 他们的大部分工作16. 重新开始