单项选择题
The centrifugal pump component responsible for converting the mechanical energy of the liquid being pumped, to that of kinetic energy is the （）.
A.electric motor B.volute C.impeller D.diffusion nozzle
单项选择题 In a refrigeration system, foaming of the crankcase oil may cause the （）.
单项选择题 Excessive scale formation in a distilling plant may result from （）.
单项选择题 Foaming of the oil in a refrigeration compressor crankcase is caused by （）.
