单项选择题
The difference between a supercharged engine and an un-supercharged engine is that （）.
A.the later B.the latter C.the former D.the farmer
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.
单项选择题 （）does it take to change the main engine from ahead to astern?
