Answer : 4. "power source"
Explanation :

Answer: D) power source Explanation: The power source such as a Battery of an IED creates an electrical charge.   What are IED's :: An Improvised Explosive Device (IED) is a bomb constructed and deployed in ways other than in conventional military action. It may be constructed of conventional military explosives, such as an artillery shell, attached to a detonating mechanism. IEDs are commonly used as roadside bombs.