单项选择题
The cylinder contains a great weight of air and is capable of burning a great quantity of fuel at（）.
A.the beginning of the compression stroke
B.the beginning of the suction stroke
C.the end of the working stroke
D.the end of the exhaust stroke
单项选择题 The cylinder and piston must be warmed up （） to a temperature of about 140 degF in standing by engine.
单项选择题 The crown is fairly thick with the cylindrical parts （） to a thinner section.
单项选择题 The cross-head shoes are white metal lined, grooves being cut horizontally on the face of the white metal to ensure （）.