单项选择题
The pour point of lubricating oils is affected the most by which of the following?（）
A.Extensive centrifuging B.Wax content C.Water content D.Acid content
单项选择题 Which of the following statements is correct concerning the viscosity of lubricating oil?（）
单项选择题 Under normal operating conditions, the rudder is hydraulically locked unless （）.
单项选择题 Saltwater is typically provided to a refrigeration system to （）.
