单项选择题
A.smaller, higher B.higher, smaller C.smaller, smaller D.higher, higher
In order to control thermal stresses, some types of mod...
单项选择题In order to control thermal stresses, some types of modern engines use pistons with（）
A.heavy wall and intensive cooling B.heavy wall and no cooling C.thin wall and no cooling D.thin wall and intensive cooling
In order to keep the oil film on the cylinder liner dur...
单项选择题In order to keep the oil film on the cylinder liner during the running-in period, the piston rings are slightly rounded（）
A.on both the external and internal top edges B.on both the external top and bottom edges C.on both the external and internal bottom edges D.on all the four edges
In some type of two-stroke engines, besides some small ...
单项选择题In some type of two-stroke engines, besides some small holes for（）, starting valve, safety valve, indicator cock, and central opening in each cylinder cover for mounting the（）
A.fuel valves；exhaust valve B.exhaust valves；inlet valve C.fuel valves；inlet valve D.exhaust valves；fuel valve
