In （） pumps a closed discharge valve will cause bursting discharge pressure.

A.discharges into a gradually widening channel
B.has stationary diffuser vanes
C.produces no kinetic energy
D.All of the above are true

A.Piston pump
B.Screw pump
C.Diffuser pump
D.Water-ring pump

A.pump entry branch
B.outlet pipe
C.impeller
D.None of the above is true