单项选择题
A.catch plates
B.dampers
C.regulating valves
D.fans
单项选择题 In extreme weather conditions, either hot or cold, control of the air conditioning plant presents （） difficulties.
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.
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.