单选题In the （） refrigeration compressor one end of the crank shaft extends through the crankcase house for connection, via a coupling or pulley, to an external drive motor.Aopen-typeBhermeticCsemi-hermeticDall the above
单选题
In the （） refrigeration compressor one end of the crank shaft extends through the crankcase house for connection, via a coupling or pulley, to an external drive motor.
A
open-type
B
hermetic
C
semi-hermetic
D
all the above
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