单项选择题
A.by trial and error B.by and large C.automatically D.very easily
Most air conditioning units have （） for adjusting the r...
单项选择题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
In extreme weather conditions, either hot or cold, cont...
单项选择题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
Because of the reduced （）in the distillation system, so...
单项选择题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
