周界

例句：

1. 1. Thecity's boundaries are marked by ariver.
   这座城市的边界被一条河标出。
2. 2. The research team set up a boundaryto keep the animals safe.
   研究团队设立了一个界限，以确保动物的安全。
3. 3. The company's boundaries were expanded due to newinvestments.
   由于新的投资，公司的边界扩大了。