23.Robots could be the first to live on Mars.机器人可能是第一批生活在火星上的(人)。

22.She’s too nervous to relax.

21.Things from Earth are hard to find.= It is hard to find thing from Earth.　　

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.