The door that is responsible for shutting off outside airflow to the cabin when maximum air- conditioning is selected is the: a. Mix door. b. Blend door. c. Air shut-off door. d. Recirculation door.

The correct answer is c. Air shut-off door.<br /><br />The air shut-off door is responsible for shutting off outside airflow to the cabin when maximum air-conditioning is selected. This door is located in the HVAC (Heating, Ventilation, and Air Conditioning) system and is designed to block the outside air from entering the cabin when the air conditioning is set to its maximum capacity. By shutting off the outside airflow, the air shut-off door helps to maintain the desired temperature and cooling inside the cabin.