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單項(xiàng)選擇題

One of the main differences between the various types of screw pumps is in the （）.

A.stuffing box diameter
B.direction of rotation of the screws
C.pitch of the screws
D.type of driving gears

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單項(xiàng)選擇題

The temperature at which water vapor in the atmosphere begins to condense is called the （）.

A.dew point temperature
B.condensation temperature
C.psychometric temperature
D.absolute humidity temperature

單項(xiàng)選擇題

The tendency for lubricating oil to thin out at high temperatures and thicken at low temperatures will be characterized by a （）.

A.low viscosity index
B.high viscosity index
C.high neutralization number
D.low demulsibility quality

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