某零件生产纲领为Q，若工艺成本中单位产品可变费用用D表示，全年不变费用用B表示，则此零件的单件工艺成本可用公式( )计算。

A．D·Q+B

B．D·Q-B

C．D+B/Q

D．D-B/Q

What does the DSC control unit do if the GMDSS radio operator fails to insert updated information when initiating a DSC distress alert?（）

A.It will abort the transmission and set off an audible alarm that must be manually reset

B.It will initiate the DSC distress alert but，as no information will be transmitted，rescue personnel will not be able to identify the vessel，its position or its situation

C.It will initiate the DSC distress alert and default information will automatically be transmitted

D.It will initiate the DSC distress alert，but any station receiving it will have to establish contact with the distressed vessel to determine its identity，position and situation