There is a question in one of the tests. Where is qui is not accepted as the answer . Why so?

Question

The question is pasted below. Why the answer should be Qu'est-ce qui and not qui while in the lesson both are used interchangably.
____________________vous avez envie de revoir ?
Who[m] do you want to see again?

Accepted Answer

Hi Richa, there are three ways to ask a question in French. Here they all are using your sentence as an example:

1) Qui est-ce que vous avez envie de revoir ? -- using "est-ce que"
2) Vous avez envie de revoir qui ? -- using intonation
3) Qui avez-vous envie de revoir ? -- using inversion

You see that if you want to use "qui" without "est-ce que", you need to use the inverted form (the third one) to ask your question, which is different from what the test expects you to answer.
Hence only the first form can be correct.
-- Chris (not a native speaker).

Answer

I am sorry i made a mistake in my question, i meant  'Qui est-ce que' and not Qu'est-ce qui.