单项选择题
In large marine diesel engines cylinder oils usually contain additives formulated to impart the （） to clean the rings and grooves.
A.inefficiency B.oiliness C.detergency D.purity
单项选择题 In general, （） is suitable for delivering small quantities at high pressure.
单项选择题 In four strokes engine, the cycle of events is completed in four strokes of （）.
单项选择题 In each cylinder cover there are two or three holes for （）
