单项选择题
A.The crankshaft B.The crankcase C.The guide-ways D.The frames
（） are formed by abrasive particles entering the bearin...
单项选择题（） are formed by abrasive particles entering the bearing and scoring the shaft.
A.Grooves B.Recesses C.Ridges D.Nips
（） are fitted in the exhaust system and facilitate char...
单项选择题（） are fitted in the exhaust system and facilitate charge removal and scavenging in each cylinder.
A.Diffusers B.Compressors C.Steam boilers D.Soot blowers
（） provide the water to the pistons.A.Pneumatic pipesB....
单项选择题（） provide the water to the pistons.
A.Pneumatic pipes B.Hydraulic pipes C.Telescopic pipes D.Operating gas pipes
