--- 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

以下属于常用中成药非处方药的是（）

A.柏子养心丸

B.乐脉颗粒

C.狗皮膏

D.木香槟榔丸

E.养血安神丸