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單項(xiàng)選擇題

Freon 12 which is used to produce intense cold is normally a （） when at atmospheric pressure and temperature.

A.liquid
B.gas
C.solid
D.water only

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單項(xiàng)選擇題

The quantity of cooled air delivered by an air conditioning unit should （） the sum of the quantity of air re-circulated to the unit and the quantity mechanically exhausted.

A.balance
B.not balance
C.be more than
D.be less than

單項(xiàng)選擇題

The shutter of the evaporator was blocked with （）, it means there was too much evaporation.

A.ice
B.wooden board
C.iron plate
D.cotton waste

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