―Excuse me, Jim. Do you have any books about Chinese history?

―Yes. ______ book above the shelf is _______ useful one.

A．The, a

B．A, the

C．The, an

D．An, the

1微米=——毫米（）。

A.10

B.O.1

C.O.001

D.O.0001

E.O.00001