英文中which的用法

英文中which的用法
主要多讲讲这种用法,我在看美剧的时候看到的：That is one classy lady,which is why I couldn't tell her.（她真是个优雅的女士,所以我对她开不了口.）

这种句法是以which指代整个句子,叫非限制定语从句,通常which前面有逗号隔开.
比如
He gave me a toy bear as birthday present,which made me very happy.
It rained heavily this morning,which made me late for school.
指的是他送我玩具熊这件事让我高兴,早上下大雨这件事让我迟到了.
当然,which指代的是什么需要具体查看句子的意思.
比如同样的
He gave me a toy bear on my birthday,which is a present I was longing for.
I came across a tiger yesterday,which was trapped in a cage.
which指代的就是主句的a toy bear和a tige