单项选择题
Most pump manufacturers recommended that the discharge piping for centrifugal pumps be （）.
A.one size larger than the pump discharge nozzle B.the same size as the pump discharge nozzle C.one size smaller than the pump discharge nozzle D.installed with a short radius elbow at the pump
单项选择题 If a refrigeration compressor is short cycling on high head pressure, you should （）.
单项选择题 What color is used to indicate the last shot of anchor chain?（）
单项选择题 A vacuum is initially created in a flash type distilling plant by（）.
