It is politely requested by the hotel management that radios __________ after 11 o'clock at night.[ ]

A. were not played

B. not be played

C. not to play

D. did not play

大量生产时之铰削，宜选用何种材质铰刀（）。

A.高碳钢

B.高速钢

C.合金工具钢

D.碳化物