Answer: B
The device is a compoent of the Rotaflow centrifugal pump head (impeller).
Souce of photo: Maquet website
The Rotaflow centrifugal pump in operation during normal saline priming
The ROTAFLOW Centrifugal Pump has a spinning rotor with flow channels which imparts rotary motion to the incoming blood, directing it through a spiral housing to the outflow port. The rotor of the ROTAFLOW Centrifugal Pump is suspended by a permanent magnetic field. The one-point sapphire bearing and the low priming volume combined with the spiral volute chamber assure a smooth blood handling and hydraulic optimized blood flow.
Reference
Further information can be obtained at the Maquet website here