If you are hunting         chance to improve yourself in English, I think the English corner will

be        ________smart choice.[ ]

A. a; a            

B. a; the            

C. the; a          

D. the; the

为了保证数控铣床连续生产，要列出加工工件所需的刀具，并用（）精确测得刀具的半径和长度。

A.千分尺

B.光学数显对刀仪

C.万能工具显微镜

D.光学测长仪