As he never raises a finger to help me with the dinner, I       the thanksgiving meal from this afternoon till now.

A．have been preparing

B．prepared

C．had been preparing

D．prepare

某岸边式取水构筑物，取水量Q=20万m³/d，24h均匀工作，取栅条厚度10mm，栅条间净距100mm，阻塞系数0.75，过栅流速v=0.4m/s．则进水孔面积应为（）m²。

A．7.5

B．8.5

C．9.0

D．9.5