The marine diesel engine is a type of diesel engine used on ships The （） of its operation is not very difficult to understand.

A.two-stroke
B.four-stoke
C.long-stroke
D.short-stroke

A.bedplate, connecting rods
B.crankshaft, the connecting rods
C.frames, crossheads
D.crankshaft, the cylinder

A.the information
B.the formation
C.the scatter
D.the friction