Final answer:
The headlights, radio, and defroster fan in an automobile are connected in parallel to the battery.
Step-by-step explanation:
The headlights, radio, and defroster fan in an automobile are connected in parallel.
In a parallel connection, each component is connected to the same voltage source and can operate independently. In this case, the headlights, radio, and defroster fan can all receive the full 12.0-V from the battery and function simultaneously.
When components are connected in series, the total voltage is divided among them, which would not be ideal for these devices in a car.