What does the term "hydraulic actuators" include?

The term "hydraulic actuators" specifically refers to devices that convert hydraulic pressure into mechanical motion. This includes hydraulic cylinders, which provide linear motion by extending and retracting, and hydraulic motors, which produce rotary motion. Both types of actuators rely on the pressure of fluid in the hydraulic system to operate. This definition aligns with the correct choice, as it encapsulates the primary functions and operational mechanisms of hydraulic actuators.

In contrast, the other options pertain to different components of hydraulic systems. Pumps and reservoirs are essential for supplying and storing hydraulic fluid but are not considered actuators themselves. Valves and gauges are crucial for controlling fluid flow and monitoring system pressure. Lastly, compressors and fluid coolers serve functions related to fluid management and temperature regulation but do not generate mechanical motion from hydraulic pressure. Thus, the focus of hydraulic actuators is on the conversion of hydraulic energy into physical work, which A accurately describes.