a defending champion的用法和样例：
- So maybe changing a key element is actually good for a defending champion, because it immediately gives them a fresh puzzle to work through.
- Defending champion Lance Mackey departs Rainy Pass.
- The defending champion Arbi succeeded in retaining the trophy.
- He shouldered off a defender and shot at goal.
- Hosts China beat defending champion Germany 3-2 in women's hockey.