1. 用方框中所给短语的适当形式填空

space travel,  have been to,  work hard,  a group of,  by spaceship

1. （1） people have seen a UFO already.
3. （2） and you'll make it.
5. （3） Ithe Summer Palace before.
7. （4） You can travel far enough.
9. （5） I'm going to haveto Mars one day.