11. We usually think ____ science subjects ____ physics, biology and mathematics.

10. Watch the stars _____ his telescope.

9. Send a massage to a friend ________ a mobile.

8. When I tried to step forward on the moon, I kept falling_______.

7. I cheered ___ immediately and floated weightlessly ____ in our spaceship cabin watching the earth become smaller and the moon larger.

6. On the earth if I fall ____ a tree I will fall ____ the ground.

5. ___ first it pushed us so hard ____ ___ our seats that we could not say anything ___ each other.

4. As the rocket rose slowly ____ the air we began to feel the pull of the earth, which is what we call gravity.

3. Whether life will continue ____ the earth ____ millions of years to come will depend _____ whether this problem can be solved.

2. It is humans that are putting too much carbon dioxide _____ the atmosphere, which prevents heat _____ escaping _____ the earth _____ space.