I know that it must be my father.过去式应该是...

问题描述:

I know that it must be my father.过去式应该是...
I knew that it must have been my father.
I knew that it must be my father.
哪个对?
我一直都认为第一句must have been 是对的
但昨天我看见一句
She knew that it must be the baker.

一楼的翻译是把it当he了.
这两句都是对的,关键看你在具体语境下具体想表达的意思了.
I knew that it must have been my father.
我就知道这事儿一直都是我父亲在做.
I knew that it must be my father.
我就知道那是我父亲.
区别就是一个是说某事的延续,一个是说某事的时点.