单项选择题
To thoroughly pump out the bilges using a horizontally mounted centrifugal pump, the （）.
A.pump must always be primed B.volute must impart a radial and rotary motion of the water suction side C.connection must guide the liquid to the lantern rings D.stuffing box should not be allowed any water leakage
单项选择题 The discharge head of a centrifugal pump will vary directly with the （）.
单项选择题 An increase in the heat load to a refrigeration system will cause （）.
单项选择题 Which of the following types of hydraulic pumps would be used in a steering system?（）
