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

## Step 1<br />The problem is about the operation of an air conditioning system in a vehicle. The air conditioning system works by controlling the airflow and temperature inside the cabin. The door that is responsible for shutting off outside airflow to the cabin when maximum air conditioning is selected is the air shut-off door.<br /><br />## Step 2<br />The mix door, blend door, and recirculation door all play different roles in the air conditioning system. The mix door blends air from the heater core with fresh air from the outside. The blend door blends air from the heater core with fresh air from the outside. The recirculation door allows the air conditioning system to recirculate air from the cabin.<br /><br />## Step 3<br />However, the air shut-off door is the one that completely shuts off the outside airflow to the cabin when maximum air conditioning is selected. This is done to prevent the outside air from entering the cabin, which could lower the temperature inside the cabin.