二
1.future
2.planted
3.environment
4.earth
5.astronaut
6.be
7.danger
8.saving
9.bored
10.scientists
三
1.will clean
2.Yes, they will.
3.We won't go out for a walk with you.
五
1.history
2.cleverer
3.themselves
4.to help
5.called
6.making
7.people's
8.ways