A(n) __ HVAC system uses an ECU to determine when to run the compressor and the amount of heat required to match and maintain the desired temperature selected by the operator. a. Automatic b. Semi-automatic c. Mechanical d. Manual

## Step 1<br />The problem is asking us to identify the type of HVAC (Heating, Ventilating, and Air Conditioning) system that uses an Electronic Control Unit (ECU) to determine when to run the compressor and the amount of heat required to maintain the desired temperature selected by the operator.<br /><br />## Step 2<br />An ECU is a type of computer that controls one or more electrical system or subsystems in a vehicle or other machine. In the context of an HVAC system, an ECU can be used to control the compressor and the amount of heat required to maintain the desired temperature.<br /><br />## Step 3<br />Among the given options, an automatic HVAC system is the one that uses an ECU to control the compressor and the amount of heat required to maintain the desired temperature. This is because an automatic HVAC system is designed to operate without manual intervention, and the ECU plays a crucial role in this by controlling the compressor and the heat output based on the desired temperature set by the operator.