Which of the following is NOT a component of a hydraulic system?

A hydraulic system is primarily composed of components that work together to transfer and manipulate fluid under pressure to perform work. The essential components include a pump, which moves the hydraulic fluid; a cylinder, where the fluid pressure is converted into mechanical force; and a fluid reservoir, which stores the hydraulic fluid.

The inclusion of a thermostat is not relevant to the basic operation of a hydraulic system. While thermoregulation may be important in some systems to manage temperature, it is not a fundamental part of the hydraulic operation itself. The main components focus on fluid movement and pressure conversion rather than temperature control. Therefore, identifying the thermostat as not being a component reflects an understanding of the core functions and structure of hydraulic systems.