a voluntary worker的用法和样例：
- She is a voluntary worker at the hospital.
- Pui Hang has been a voluntary worker since primary school and has joined various kinds of voluntary service, including serving people with mental disability, elderly, patients in the hospital, etc.
- He made a voluntary statement to the police.
- The prisonermade a voluntary statement.
- The organization is run on a voluntary basis.
- A voluntary acknowledgment of truth.