Pick up the correct statement from the following regarding radial flow centrifugal pumps :

• A. These are provided with volute type or turbine type casings
• B. In involute type of radial flow centrifugal pump, the impeller discharges into a gradually expanding spiral casing
• C. In turbine type of radial flow centrifugal pumps, the impeller is surrounded by stationary guide vanes to reduce the velocity of water
• D. All the above.