bookはどれ？って英語でなんて言うの？

この場合は「bookはどれ」は英語で Which one's the book?と言います。 Which one is* the book? Which one's the apple? Which one's the chair? 他に使えるフレーズは Touch the book/Touch the apple や Where's the book?/Where's the apple? です。 Where is* the book?