guard gap

例句：

1. 1. The police officers stood guard at the entrance of the stadium.
   警察在体育场入口站岗。
2. 2. The border between our two countries is very strict.
   我们两国之间的边界非常严格。
3. 3. The demarcation line was clearly marked on the map.
   地图上清晰地标出了分界线。