地界标

例句：

1. 1. The boundary between our two countries is clear.
   我们两国的边界是清晰的。
2. 2. The scientist marked the boundary of the new land with a flag.
   科学家用一面旗帜标记了新土地的边界。
3. 3. The boundary line between the two countries has been disputed for years.
   两国之间的边界线多年来一直有争议。