Please choose the correct ending to complete the given sentence: Home and Garden: [header] How to understand the basic operation of the home air conditioning system [title] Understand what the compressor does. [step] The compressor is the heart of a basic home air and heat unit. It pumps vapor refrigerant through the system and maintains the internal pressure of your home unit based on the temperature of it surroundings.

Ending1: [substeps] The compressor requires a regular indoor refrigerator for it to operate. The compressor shouldn't be heated more than 1800-2500 degrees fahrenheit. Ending2: It inflates and insulates the warm, humid air inside the unit. In order to function properly in your home, you must develop a universal thermostat that controls the temperature and heats your home continuously. Ending3: Most homes do not have any type of manual compressor. Basic compressors do not have any type of control or direction. Ending4: [title] Understand the role of the condenser. [step] This is where the refrigerant goes once it leaves the compressor.

Answer format: ending1/ending2/ending3/ending4