单项选择题
The viscosity of an oil is a measure of its （）.
A.weight B.internal friction C.demulsibility
单项选择题 The pour point of lubricating oils is affected the most by which of the following?（）
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 （）.
