Final answer:
The thermostat regulates supplementary electric heat in a heat pump system based on outdoor temperature.
Step-by-step explanation:
The device that controls the supplementary electric heat according to outdoor temperature in a heat pump system is the thermostat. The thermostat is designed to sense the outdoor temperature and regulate the use of supplemental electric heaters to maintain a desired indoor comfort level.
As the outdoor temperature decreases, the thermostat activates the supplementary heat to ensure efficient and sufficient heating of the space.
The device that controls the supplementary electric heat according to the outdoor temperature is the thermostat.
In a heat pump system, the thermostat senses the outdoor temperature and adjusts the operation of the heat pump to provide additional electric heat when the outdoor temperature is too low to meet the heating demands. This ensures that the indoor temperature remains comfortable.
Therefore answer is c) Thermostat.