An Improvised Explosive Device (IED) is a bomb constructed using unconventional means. The fundamental components generally required for a functional IED are: 1. Explosive This is the main charge that produces the explosion. 2. Detonator/Initiator This is a smaller charge or mechanism used to trigger the main explosive charge. 3. Initiating System This system activates the detonator. It often includes a power source (like a battery), a switch, and wiring for electrical detonation, which is very common in modern IEDs due to its versatility (e.g., timer, remote control). While non-electric initiation systems exist (like fuses), a battery is a common and necessary component for electrically initiated IEDs. Given the options, all three listed items are standard components for a widely used type of IED construction.