Which type of pump operates by compressing fluid and displacing it?

The correct choice, which is the piston pump, operates by the principle of compressing fluid and displacing it. In a piston pump, the piston moves within a cylinder to create pressure, which pushes the fluid out of the chamber. This method is straightforward and effective for a range of applications, notably when high pressure is required.

Piston pumps are known for their ability to handle thick and viscous liquids well, making them suitable in various settings, including agricultural and industrial applications where the manipulation of liquid volume and pressure is crucial. The mechanical action of the piston ensures a positive displacement of fluid, allowing for precise control over flow rates.

In contrast, diaphragm pumps, while also capable of displacing fluids, utilize a flexible diaphragm to create a pumping action through a series of pressure changes rather than direct compression as with piston pumps. Centrifugal pumps, on the other hand, rely on rotational energy to move fluid through the pump, which does not involve compressing the fluid like a piston does. Gear pumps use rotating gears to create flow and pressure but also do not involve the straightforward compression mechanism characteristic of piston pumps.

Thus, the piston pump is distinguished by its method of fluid displacement through compression, making it the appropriate choice in this context.