单项选择题

A.can be started at low temperature and are free from p……

In modern installations, the main engine and the standby auxiliary engines（）

A.can be started at low temperature and are free from preheating
B.usually are preheated by steam before being started
C.are kept at a constant temperature and free from preheating
D.are kept at a low temperature to save energy

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单项选择题In order to maintain a constant outlet water temperature of 80-85℃ from the engine, a three-way valve is installed（）

A.at the jacket cooler outlet to control the flux through the engine
B.at the jacket cooler outlet to control the flux through the cooler
C.at the engine outlet to control the flux through the engine
D.at the engine inlet to control the flux through the engine

单项选择题About the jacket water, that of the auxiliary engines usually（） is circulated by pumps, and the main engine usually （）

A.an engine-driven；as well
B.an engine-driven；has an independent pump
C.an independent；as well
D.an independent；has an engine-driven pump

单项选择题The cooling system（） needs least maintenance work for in this kind of system（）

A.open；the minimum components
B.open；the high cooling efficiency
C.central；there are more coolers and a extra set of pumps
D.central；there is only one component contacts seawater

单项选择题An alarm device inserted between the deaerating tank and the expansion tank can notify the on-watching crew that （）

A.the expansion tank is lack of water
B.the expansion tank is over flowing
C.there is something wrong with the cooling system
D.there is something wrong with the engine

单项选择题As an alternative to the conventional seawater cooling system, is based on principles about cooler locations, （）flow control and preheating, but with a central cooler and one additional set of pumps（）.

A.the central cooling system, different
B.the central cooling system, the same
C.the open cooling system, different
D.the open cooling system, the same