单项选择题
A.The wearing rings are excessively worn
B.The suction strainer is clogged
C.The discharge valve is clogged
D.The shaft is worn
单项选择题 The sudden reduction of pressure occurring within the crankcase of a refrigeration compressor during starting causes the （）.
单项选择题 One of the consequences in continuing to operate a centrifugal bilge pump with the discharge valve closed, is that the （）.
单项选择题 Which of the following statements is correct concerning a typical shipboard multi-coil refrigeration system?（）