根据句意，用括号内所给单词的适当形式填空。

1.  Which city has ____________ ( little ) air pollution, Wuxi or Nanjing?

2.  Next Sunday will be my brother’s __________ ( nine ) birthday.

3.  The boy is talented and ______________ ( energy ), so we all like him.

4.  Last Saturday evening Helen ran into a friend of __________ ( she ) at the shopping centre.

5.  Could you tell me how many ____________ ( shelf ) there are in your school library?