Which of the following pumps are self-priming, and can deal with liquid from a level below the pump（）
(1) ejector
(2) screw
(3) centrifugal
A.(1)only
B.(1)and(2)
C.(1),(2)and(3)
D.(2)and(3)
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A.centrifugal
B.plunger
C.injector
D.water
A.discharges into a gradually widening channel
B.has stationary diffuser vanes
C.produces no kinetic energy
D.All of the above are true
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