单选题Under normal conditions, the quantity of air circulation becomes less and less.What is the reason?（）Adirty delivery ductsBtoo much refrigerantCthe fouling filtersDhigh temperature outside
单选题
Under normal conditions, the quantity of air circulation becomes less and less.What is the reason?（）
A
dirty delivery ducts
B
too much refrigerant
C
the fouling filters
D
high temperature outside
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