含I don't know 的几个宾语从句问题

含I don't know 的几个宾语从句问题
I don't know ___.
答案是where my class teacher lives now
为什么不能是where my class teacher is living now
I don't know ___.
答案是how well I did in the exam
为什么不能是if I had passed the exam
这个我有猜测下……因为没有时间点所以不需要用过去完成时?就是说如果是if I passed the exam就可以么?