单句改错。

1. Your friend comes to school is very upset. _________

2. Tell your friend that you are concerning about him. _________

3. While walk the dog, you were careless and it got loose. __________

4. Join the examination and you'll get a chance. __________

5. Yesterday I got my bike repair. __________

减压塔的塔径发生变化，但塔板间距不发生变化。