ANS:A - high head.

Multistage centrifugal pumps are generally used for high head applications. Here's why:

• High Head: Multistage centrifugal pumps are designed to generate high pressure or high head by using multiple impellers arranged in series within the same pump casing. Each impeller adds kinetic energy to the fluid, and this energy is converted into pressure as the fluid passes through each stage. This configuration allows multistage pumps to achieve higher pressures than single-stage pumps.
• Low Head but High Discharge: For low head applications but high discharge, single-stage centrifugal pumps are typically sufficient and more economical. Multistage pumps are not usually required for such applications unless there is a need for both high head and high discharge.
• Highly Viscous Liquid: For highly viscous liquids, specialized pumps such as positive displacement pumps or screw pumps are generally used due to their ability to handle high viscosity fluids effectively.
• Slurries of High Solid Concentration: For slurries with high solid concentration, pumps designed specifically for handling solids, such as slurry pumps or dredge pumps, are typically used. These pumps are designed with features like large impeller passages and wear-resistant materials to handle abrasive and solid-laden fluids.