英语翻译They cannot store water,and their reliance on an entirely unexceptional kidney results in a rate of water loss through renal function significantly higher than that of desert rats.through是谓语吗 that of是指前文的描述的rats，

英语翻译
They cannot store water,and their reliance on an entirely unexceptional kidney results in a rate of water loss through renal function significantly higher than that of desert rats.
through是谓语吗 that of是指前文的描述的rats，那为什么用that of来指代呢？

他们不能储存水,由于依赖于非常普通的肾,导致水流失比跳鼠严重.
through不是谓语,results 才是.因为这里有比较级,所以用that 指代