a cheer leader的用法和样例：
- My girl friend is a cheer leader.
- A cheerful leader invariably wins more cooperation than a grim or gloomy one.
- You see,I was asked to be the cheer leader.
- You see, I was asked to be the cheer leader.
- A cheer rose from the south stand(s).
- A cheer went up in the auditorium.