给下列句子选择句意相同的选项。① The book is mine. {#blank#}1{#/blank#} A. It's Mike's book.
② The book is Amy's. {#blank#}2{#/blank#} B. The book is theirs.
③ It's their book. {#blank#}3{#/blank#} C. Its' Amy's book.
④ The book is Mike's. {#blank#}4{#/blank#} D. It's my book.