单项选择题 Large crosshead type engine generally has two lubrication systems, a function performed only by cylinder oil system is（）

单项选择题 In some diesel engine designs,（）the injection of cylinder oil is timed to impinge when the piston and only impinge on（）

单项选择题 （）diesel engines generally have two systems of lubrication:（）a total loss system feeding and a circulating system lubricating the running gear and cooling the pistons.