单项选择题
A.The medium speed 4-stroke trunk piston engine
B.The low speed 2-stroke crosshead engine
C.The medium speed 2-stroke crosshead engine
D.The low speed 4-stroke trunk piston engine
单项选择题 The difference between a supercharged engine and an un-supercharged engine is that （）.
单项选择题 （）, the following possible causes should be investigated.
单项选择题 We have planned to remove the piston with the help of assistant engineers during the cargo unloading, while the vessel （）port Shanghai.