CN cycle

例句：

1. 1. The CN cycle is a model that describes the relationship between economic growth and environmental degradation.
   循环周期模型描述了经济增长与环境退化之间的关系。
2. 2. The CN cycle has been studied extensively in China, with various theories proposed to explain its causes and effects.
   中国的循环周期研究非常广泛，提出了各种理论来解释其原因和影响。
3. 3.In recent years, there has been growing interest in the CN cycle as it relates to sustainable development.
   近年来，随着可持续发展的兴起，人们越来越关注循环周期。