______ book on the desk is ______ useful one.

A. The, an                    B. A, a                   C. The, a               D. The, 不填

________ book on the desk is ________ useful one.

A. The; an

B. A; a

C. The; a

D. The; /

________ book on the desk is ________ useful one.

A. The; an

B. A; a

C. The; a

D. The; /

     book on the desk is    useful one.

________ book on the desk is a useful（重要的）one.

　　A. A B. An C. The D. /

--- Look at ______ book on the desk . Is it ______ useful one ?

--Yes, it is . In the book there is much advice on how to learn math well.

A．a, the            B．the, a             C．the, an            D．a, an

--- Look at ______ book on the desk . Is it ______ useful one ?

---Yes, it is . In the book there is much advice on how to learn math well.