Question

an electric motor.
an armature.
a solenoid.
a battery.

Explanation:

To solve this, we analyze each option:

• An electric motor converts electrical energy to mechanical energy, not a source of electricity.
• An armature is part of a motor/generator, not a power source.
• A solenoid is an electromagnet, not a power source.
• A battery is a device that stores and provides electrical energy (chemical energy to electrical energy), so it's a source of electricity.

Answer:

a battery.