英语，一小语法

Anthropology is a science in that anthropologists use a rigorous set of methods and techniques to document observations that can be checked by others.

这句话中in that...是什么从句？句子结构应是怎样的？

in that = because（因为），in that 引导的是原因状语从句。in that 后面都是从句。

in that 引导的应该是定语从句，修饰先行词a science. 严格地讲，这儿用which才对。