What should you do after moving the heater switch to defrost?

Answer: B — Check for air flow

After moving the heater switch to defrost, it is essential to check for air flow. This step ensures that the defrost system is functioning properly, allowing you to see clearly through your windshield by directing warm air to it, which helps eliminate condensation or frost. Ensuring adequate air flow is crucial for maintaining safety while driving in adverse weather conditions, as visibility can significantly impact your control of the vehicle. The action of checking air flow verifies that the heater and defroster systems are operational and can warm the windshield effectively. This process is part of a comprehensive pre-trip inspection that emphasizes safety and preparedness before getting on the road.