單項選擇題To function properly, oil control rings used on a diesel engine piston must distribute sufficient oil to all parts of the cylinder wall and must also（）.

A.prevent any lubricant from reaching
B.prevent excessive lubrication from reaching the combustion space
C.Provide metal-to-metal contact to seal the cylinder against blow-by
D.assure a positive means of scraping carbon accumulation from the cylinder


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1.單項選擇題Which of the listed cylinder liner surface conditions indicates proper lubrication?（）

A.Dull black appearance
B.Bright appearance
C.Thin layer of lacquer
D.Thick oily film

2.單項選擇題In an operating diesel engine, which of the following condition is an indication of a leaking air starting valve?（）

A.noise coming from that air starting valve
B.continuous operation of the starting air compressor
C.zero air pressure in the air starting system
D.overheated starting air pipe to the cylinder head

3.單項選擇題An over-speed trip serves to （）

A.stop the engine by cutting off the cooling water supply
B.stop the engine by closing the air intake
C.slow the engine but not stop it
D.slow the engine to half of normal load

4.單項選擇題Oil control rings used in two-stroke/cycle diesel engines are located near the bottom of the piston skirt in order to （）

A.increase the liner area covered by the oil film
B.maintain an oil film on the lower liner where scuffing is prevalent
C.keep excess oil away from intake and exhaust ports
D.help cushion piston skirt side thrust by providing a hydrodynamic oil wedge

5.單項選擇題In describing basic diesel engine operation，the term ‘event’ refers to （）

A.the production of high pressure gases
B.the removal of expended combustion gases
C.the admission of air to the cylinder
D.all of the above