单项选择题
The volute pump is one in which the impeller （）.
A.discharges into a gradually widening channel B.has stationary diffuser vanes C.produces no kinetic energy D.All of the above are true
单项选择题 Which of the following pumps belongs to centrifugal pump?（）
单项选择题 The pump discharge pressure will be considerably higher than the pressure at the （）.
单项选择题 What is the purpose of a relief valve?（）
