guard timber of bridge

例句：

1. 1. Thesoldiers were guarding the border.
   士兵们正在守卫边境。
2. 2. She guarded her secret well.
   她很好地保守了她的秘密。
3. 3. Theguards were vigilantin their duty.
   警卫们警惕地履行他们的职责。