Which of the listed cylinder liner surface conditions indicates proper lubrication?（）

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

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

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