1. 用括号内所给词的适当形式填空

1. （1） In autumn, the (leaf) turn yellow.

3. （2） What do you think is (useful) invention in the world?

5. （3） I think it would be (good) to have a TV set than to have a radio.

7. （4） —What is the knife used for?
   

   —It's used for (cut) things.
   

9. （5） It is worth (mention) that Nanjing has entered Top 10 Appealing Chinese Cities.