20.A very popular form of entertainment is online games.

19.The surface of Mars is more like the surface of Earth than any other planet in our solar system.

18.It takes Mars about two years to revolve completely around the sun.

16.It worries me.

　 ★17. It would be great to have robots do all the work for us.

15.50% of the students would like to move out of Earth.

14.We could get ill from living there.

13.I am wondering if/whether there will be many people willing to move to Mars.

12.Every student will have a computer at home (connecting to an inter-planet computer network.)

10.The gravity on Mars is only about three-eighths of the gravity on Earth.

　★11.There will be many different designs for settlers to choose from.

9.However, it is not sure if these plants could produce water.