she went home after she had typed the letter为什么用had而不是has,这儿是第三人称啊?

问题描述:

she went home after she had typed the letter为什么用had而不是has,这儿是第三人称啊?
句子来源于新概念120课,课后习题A.例句

she went home 是主句 after she had typed the letter 是表示时间状态,所以.
通俗点说,主句里面是过去式,那么修饰主句的句子也用过去式、过去完成时,过去将来时等过去时态.过去时态没有第三人称.都是had
还有什么需要解释的吗