高一英语语法--定语从句1.We are just trying to reach a point _____both

高一英语语法--定语从句
1.We are just trying to reach a point _____both sides will sit down together and talk.
A.where B.that C.which
(主要说明为什么不选B）
2.The school is the one(that/which)he visited yesterday
The school is the one(that/which)he studied at last year
The school is the one(where/at which)he studied last year
这三句有什么区别,为什么用的关系代词不一样
【不懂者请勿胡乱作答,保证正确率】