ارجو الافادة من السادة الزملاء

[الاسوانى محمد حسين]

dear colleaues;
in longman ex unit 13 grammar. sentence no(9)

I have no idea who _____ was at the door.

a) who b) which c) where d) that
it was written that the right answer is (that) please , would you be patient and tell why ???
thank you for your time.

[الاسوانى محمد حسين]

is there anyone who can help?

[The Ocean]

Study this:
A:Who was that at the door?
B: I have no idea who that was at the door.

[Mr. Ayman Osman]

المشاركة الأصلية كتبت بواسطة The Ocean

Study this:
A:Who was that at the door?
B: I have no idea who that was at the door.

I agree with you very much for your wonderful explanation

[الاسوانى محمد حسين]

can't we say " who was at the door?
what is the meaninig of
' that
' here?
could you explain a littel more please