You are the (one/ones) who (are/is)

Question

I'm talking about both singular and plural form of "you", so I hope the provided answer will include both answers.

Singular You

You are the one who 《are/is》...

I'm equating the "singular you" with the "singular one" and both words have different conjugation of "to be" i.e. are and is respectively, I suppose. I believe I would choose is in this case. So it would be:

[1] You are the one who is ...

However, I'm not sure since I believe this construction sentence below is correct (don't ask me why because I don't know the reason, it just makes sense to me):

I see you who are sweeping the floor right now.

My point is, I'm not sure whether the conjugation has to agree with "the one" or "you" or either way is correct I don't know.

Plural You

You are (all) the 《one/ones》who 《is/are》...

My guess about the correct writing is like this:

[2] You are (all) the ones who are ...

Are my guesses [1] and [2] above correct grammatically? Is there another possible combination I haven't mentioned which is correct? If this doesn't make sense to you, could you please suggest another construction to avoid confusion as to either singular or plural form of "you" which I want to address?

Thanks in advance!

Answer 1

Yes, all of your "guesses" are correct.

The verb in the relative clause must agree with its subject (in this case, the relative pronoun "who"), which must agree with its referent. In the first sentence, the referent ("the one") is third person singular, so "who" must be the same:

You are the one who is ...

In the second sentence, the referent ("you") is second person singular, so "who" must be the same:

I see you who are sweeping the floor right now. (Note that although this is correct, it's not common.)

In the third sentence, the referent ("the ones") is third person plural, so "who" must be the same:

You are (all) the ones who are ...