1. What are these? These are books.

2. What are those? Those are books.

3. What are they? They're books.

I'm curious if I always can, regardless of the question, answer "They're books". For example: What are these? They're books. (instead of "These are books"). What are those? They're books. (instead of "Those are books").

Hello NG,

It seems to me that "They're XYZ" might well be the most likely answer, in most situations.

Best wishes,

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But "these are ..." and "those are ..." are also correct, right?

Yes, they're correct; but repeating the pronoun seems to create a more emphatic version.
OK, thanks.
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