高中虚拟语气问题4帮忙看下吧?

题目

高中虚拟语气问题4帮忙看下吧?
The purpose of the exam was to test the student is mastery of knowledge they had studied.帮忙分析下结构成分句型 purpose mastery knowledge 这三个单词什么意思 谢谢O(∩_∩)O

答案

主语 the purpose of the exam 考试的目的
谓语 test
从句 the student is mastery of knowledge they had sudied 学生已经掌握了他们所学的只是
从句里又套了一个 定语从句 修饰knowledge 后面省略了which