The trees are on the school campus.They have lost their leaves.两句合并成一句,用定语从句.

The trees are on the school campus.They have lost their leaves.两句合并成一句,用定语从句.
1.The trees which are on the school campus have lost their leaves.2.The trees that have lost their leaves are on the school campus.怎样确定主句,从句呢?1,2号句哪个是对的?
在合并两个小句时如何确定那个做主句和哪个做从句。
不是分辨一个定语从句的主句和从句。