What factor affects the efficiency of a pump?

The efficiency of a pump is influenced by multiple factors, making the choice that includes "all of the listed factors" correct.

Fluid viscosity plays an important role because it affects how easily the fluid can be moved through the pump. A higher viscosity fluid can lead to greater energy losses due to increased friction within the system, impacting the overall efficiency.

The type of impeller is another crucial factor. Different impeller designs can enhance or hinder the flow characteristics of the fluid being pumped. For instance, an impeller that is optimized for a specific type of fluid can ensure more efficient energy transfer and reduced turbulence.

Pump speed is also a significant factor in determining efficiency. Increasing the speed of the pump generally increases flow rate, but it can also lead to greater energy consumption and potentially diminish efficiency if the pump is not operating within its optimal range.

Since all of these factors—fluid viscosity, type of impeller, and pump speed—contribute uniquely to the efficiency of a pump, the option that states "all of the listed factors" encompasses the comprehensive nature of the influences affecting pump efficiency.