Final answer:
The correct answer is C. Pressure switch.
A pressure switch is a protective device that prevents the operation of a unit when there is inadequate fluid flow. It acts as a sensor and control device in various applications such as HVAC systems, water pumps, and hydraulic systems.
Step-by-step explanation:
A protective device that prevents the operation of a unit when there is inadequate fluid flow is called a pressure switch. A pressure switch is a device that opens or closes an electrical circuit based on the presence or absence of adequate fluid pressure. It acts as a sensor and control device in various applications such as HVAC systems, water pumps, and hydraulic systems.
For example, in a water pump system, if the pressure drops below a certain level indicating inadequate fluid flow, the pressure switch will open the circuit and stop the pump from operating. This prevents damage to the pump and other components.
Therefore, out of the given options, the correct answer is C. Pressure switch.