natural grade

例句：

1. 1. The company has decided to implement a natural grade system for its employees.
   该公司决定为员工实施一个自然等级制度。
2. 2.The natural grade of the soil is an important factor in determining the yield of crops.
   土壤的自然等级是决定农作物产量的一个重要因素。
3. 3.The natural grade of the product is determined by its quality and performance.
   产品的自然等级由其质量和性能决定。