求助一个英语句子的语法分析

Question

It (ground underfoot) absorbs most of the water it contains from rivers.
后面的 it contains from rivers 是什么语法现象？

Answer 1

这句话译为：地下空间里的水大部分来自于河流。it contains from rivers是 the water的定语从句，句中缺少宾语，所以可以用关系代词that或which作contain的宾语，而在这种情况下，that和which可以省略。

Answer 2

定语从句，省略了引导词which
鉴定完毕

Answer 3

其实这类句子不是太规范，不必太一板一眼地去分析它，自己感觉一下，后面的it是用来解释说明water的，所以是定语

Answer 4

省略that、which的定语从句。
It (ground underfoot) absorbs most of the water which it contains from rivers.