单选题Before charging a refrigeration unit, the refrigerant charging lines should be（）Aflushed with clean refrigerant oilBpurged with the refrigerantCwashed with an ammonia and alcohol solutionDgrounded to compressor
单选题
Before charging a refrigeration unit, the refrigerant charging lines should be（）
A
flushed with clean refrigerant oil
B
purged with the refrigerant
C
washed with an ammonia and alcohol solution
D
grounded to compressor
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