单项选择题
In an auxiliary diesel engine, the reason for knurling the piston skirt is to（）
A.improve skirt lubrication B.allow for expansion C.transmit forces evenly D.improve the piston seal
单项选择题 Which of the listed design features is found in an exhaust valve and NOT in an intake valve?（）
单项选择题 A diesel engine cylinder head can crack as a result of （）
单项选择题 In large, low-speed, main propulsion diesel engine, position ring groove wear usually occurs at the（）
