Final answer:
The condenser is the component of a system that changes the refrigerant from a high-pressure vapor to a high-pressure liquid when the system is operating.
Step-by-step explanation:
When a system is operating, the component that changes the refrigerant from a high-pressure vapor to a high-pressure liquid is the condenser (b). The electrically driven compressor first raises the temperature and pressure of the gas and forces it into the condenser coils located inside the heated space. Due to the gas's temperature being higher than that of the room, a heat transfer occurs, causing the gas to condense into a liquid. This liquid, now a high-pressure liquid, is further processed as it moves through the system, returning to the outdoor evaporator coils after passing through a pressure-reducing valve.
In this cycle, the condenser is responsible for the condensation of the high-pressure vapor into a liquid, significantly contributing to the cycle by which the system can perform its cooling function effectively.