circulation theorem

例句：

1. 1. The bloodcirculates through the body to deliver oxygen and nutrients to every cell.
   血液通过循环系统输送氧气和营养物质到每个细胞。
2. 2. The river's water circulation is crucial for the ecosystem.
   河流的水循环对生态系统至关重要。
3. 3. The new policy aims to improve the efficiency of the city's transportation system.
   新政策旨在提高城市交通系统的效率。