单项选择题
A.stuffing box diameter
B.direction of rotation of the screws
C.pitch of the screws
D.type of driving gears
单项选择题 The temperature at which water vapor in the atmosphere begins to condense is called the （）.
单项选择题 The tendency for lubricating oil to thin out at high temperatures and thicken at low temperatures will be characterized by a （）.
单项选择题 Increasing the speed of a rotary pump above its rated speed will result in which of the following conditions to occur?（）