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1. My brother has borrowed 5 books.

К подлежащему: Who has borrowed 5 books?

Разделительный: My brother has borrowed 5 books, hasn't he?

2. Jane lost her favourite book.

К подлежащему: Who lost their favourite book?

Разделительный: Jane lost her favourite book, didn't she?

3. Kate and Leo are reading fairy tales now.

К подлежащему: Who is reading fairy tales now?

Разделительный: Kate and Leo are reading fairy tales now, aren't they?