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單項(xiàng)選擇題

Most air conditioning units have （） for adjusting the ratio of recirculated fresh airCare must be taken not to reduce the fresh air so that stuffiness or smells arise.

A.catch plates
B.dampers
C.regulating valves
D.fans

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單項(xiàng)選擇題

In extreme weather conditions, either hot or cold, control of the air conditioning plant presents （） difficulties.

A.few
B.little
C.a little
D.less

單項(xiàng)選擇題

Because of the reduced （）in the distillation system, some of the sea water boils as it flows through the tubes of the evaporator.

A.pressure
B.temperature
C.density
D.volume

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