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單項(xiàng)選擇題

An instrument that maintains a continuous record of humidity changes is called a（）.

A.thermometer
B.barometer
C.hygrograph
D.thermograph

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單項(xiàng)選擇題

An instrument that indicates wind direction is known as a(n)（）.

A.weather vane，wind vane or wind sock
B.hydrometer
C.hygrometer
D.sling psychrometer

單項(xiàng)選擇題

All of the following steps are taken in starting a centrifugal pump，EXCEPT to（）.

A.set the relief valve
B.check the lubrication system
C.vent the pump casing
D.open the pump suction and discharge valves