单项选择题
Foaming of the oil in a refrigeration compressor crankcase is caused by （）.
A.refrigerant boiling out of solution from the lube oil B.liquid refrigerant flooding the compressor and system C.lube oil viscosity being reduced by refrigerant dilution D.compressor suction pressure suddenly increasing
单项选择题 Which of the listed characteristics can be applied to R- 12 vapor?（）
单项选择题 The percentage of impurities in a specific fuel oil sample is determined by （）.
单项选择题 If your vessel bums 8 tons of fuel per hour at 15 knots, how many tons per hour will it burn at 18 knots?（）
