I don't know___they have passedI don't know___ they have passed the exam1.what2.if 3.when4.where

I don't know___they have passed
I don't know___ they have passed the exam
1.what
2.if
3.when
4.where

2
从句成分完整
表示带有疑问,if此处同whether

2
if是是否的意思

2
我不知道他们是否通过了考试。

2 我不知道他们是否已经通过考试

if
I don't know if they have passed
我不知道他们是否通过了

1

2，I don't know说明他不确定，而if有是否的意思