A （）is the foundation of the engine, without the support of which the shaft alignment in particular, and engine structure as a whole, would inevitably be lost.

A.“prepare to stop the engine”
B. “assemble an engine on its bedplate”
C. “make an engine ready for starting”
D. “dismantle an engine”

A．by using of fresh water
B．with compressed air
C．by using of sea water
D．with chemical compound