in active service

例句：

1. 1. The soldiers are in active service to protect the country's borders.
   士兵们正在积极服务以保护国家的边境。
2. 2. The police are in active service to maintain public order.
   警察正在积极服务以维护公共秩序。
3. 3. The firefighters are in active service to put out the fire.
   消防员正在积极服务以扑灭火灾。