Students need a high school diploma if they want to go to college.包含什么语法现象

Students need a high school diploma if they want to go to college.如果学生想上大学,需要有高中文凭.这个句子包含的语法现象就是条件状语从句.the first of which is September through December这个句子是个定...完整的是什么样Students need a high school diploma if they want to go to college.

和
the first of which is September through December

这两句话是连在一起的吗？不是不是那你把第二句的完整句子发过来看看，因为第二句是一个不完整的定语从句，还缺少半句。The school year is divided into two semesters, the first of which is September through December, and the second January through May.The school year is divided into two semesters, the first of which is September through December, and the second January through May.

本学年分为两个学期，第一学期从九月到十二月，第二学期从一月到五月。