circulation area

例句：

1. 1. The blood circulates through the body to deliver oxygen and nutrients.
   血液通过身体循环输送氧气和营养物质。
2. 2. The river is a natural circulation system that carries water from the mountains to the sea.
   这条河流是一个自然的循环系统，将水从山区输送到大海。
3. 3.Circulation rates are important indicators of health.
   循环率是健康的重要指标。