yield guard

例句：

1. 1. The policeman was a good yield guard at the airport.
   这位警察在机场担任了很好的警卫工作。
2. 2.The soldiers were ordered to stand by as a yield guard.
   士兵们被命令作为警卫站岗待命。
3. 3.The security guards were vigilant and ready to intervene if needed.
   保安人员警觉并随时准备介入。