sentence construction - "whose apple is that" or "whose is that apple"

Are both of the following sentence structures correct?

Whose is that apple?

Whose apple is that?

Can the word order be shuffled like this? There does not seem to be missing any clarity in either sentence.

I guess I would use such different word ordering to be able to put emphasis on certain words:

Whose is that apple?

Whose apple is that?

But is it allowed?

Answer

Both are correct. In:

• Whose is that apple?

"whose" is an interrogative pronoun and, syntactically speaking, the subject complement (SC). This can be demonstrated by the fact that the natural reply will be:

• It (=That apple)'s mine. ("mine" is a possessive pronoun and the SC of the sentence).

Instead, in:

• Whose apple is that?

"whose" is an interrogative determiner that accompanies "apple". The whole phrase, "whose apple", is the SC. Proof of this is that the natural reply will be:

• It/That's my apple. (where "my" is a possessive determiner that modifies "apple", with the whole phrase, "my apple", being the SC of the sentence.)