A Pressure Regulator is a device that:

A pressure regulator is specifically designed to control and reduce the pressure of gas before it is delivered to a downstream system or appliance. When gas enters the regulator, it typically comes in at a higher pressure, and the regulator's function is to maintain a consistent, lower pressure at the outlet.

This is crucial because many gas appliances operate efficiently and safely at specific pressure levels. If the gas pressure were to remain too high, it could potentially damage appliances or create unsafe operating conditions. The design of a pressure regulator includes mechanisms that adjust the gas flow in response to variations in upstream pressure and demand from downstream appliances, ensuring that the outlet pressure stays within safe and usable limits.

Therefore, the correct answer accurately describes the primary function of a pressure regulator as reducing gas pressure from the inlet to the outlet, ensuring safe and effective operation of gas systems.