单项选择题
The ability of lubricating oils to resist viscosity changes during temperature changes is indicated by the（）
A.American Petroleum B.Institute number viscosity index number C.Seconds Saybolt Furol number D.Seconds Saybolt Universal number
单项选择题 The in the steering gear move the rudder to the required angel（）
单项选择题 Positive displacement, helical gear pumps are well suited for pumping oil because （）
单项选择题 One of the reasons that causes oil flowed from sludge outlet of a self-cleaning purifier is （）
