What type of IED utilizes commercial explosives as a main charge?

The selection of commercially available explosives IEDs as the correct answer is based on the fact that these devices specifically incorporate explosives that can be obtained through legal channels for legitimate uses, such as construction and mining. Commercial explosives are manufactured to meet safety regulations and are designed for practicality in these industries, which makes them accessible to those who may wish to construct an IED.

In terms of construction, commercially available explosives are typically formulated to provide substantial energy release and effective detonation, making them suitable for illegal use in IEDs. This choice aligns with the defining characteristics of IEDs that utilize recognized explosive materials, distinct from the other types listed.

The other options, while they may refer to various IED compositions, do not specifically highlight the use of commercially available explosives as their main charge. Homemade explosives IEDs usually refer to improvised materials that the individual creates or synthesizes. Military-grade explosives IEDs denote explosives that are manufactured for military purposes and are generally much harder to obtain without proper authorization. Bespoke fabrications would suggest highly specialized designs and may not directly refer to the use of commercially sourced materials at all. Hence, the emphasis on commercially available explosives identifies the focus of the question effectively.