a tour of duty的用法和样例：
- He was asked to go back for a third tour of duty.
- It took two years to achieve agreement across the community, McConnell relates, but now senior leaders in intelligence agencies must serve a tour of duty outside of their parent organizations.
- He conducted us on a tour of the castle.
- We are going on a tour of the city this afternoon.
- After that we went on a tour of the plant.
- The group goes on a tour of italy.