Which of the following is a source of energy in an automobile's electrical system?

The source of energy in an automobile's electrical system primarily comes from both the battery and the AC generator. The battery serves as the initial power source that provides electrical energy for starting the engine and powering electrical accessories when the engine is not running. It supplies direct current (DC) that is essential for components like the starter motor, lights, and electronics.

On the other hand, the AC generator, commonly referred to as an alternator in automotive applications, generates alternating current (AC) when the engine is running. This AC energy is then converted to DC, which is used to recharge the battery and power the vehicle's electrical system when the engine is operational. The alternator must maintain the battery's charge while providing power to various electrical components.

By recognizing that both the battery and the AC generator (alternator) are critical in producing and supplying electrical energy to the vehicle, the choice that encompasses both sources accurately reflects the functions of an automobile's electrical system.