Which of the following can be classified as a secondary explosive?

RDX, or Research Department Explosive, is classified as a secondary explosive due to its properties and behavior when subjected to an initiating force. Secondary explosives, such as RDX, require a detonator or similar high-energy initiator to detonate, meaning they are less sensitive to heat, shock, and friction when compared to primary explosives.

RDX is a powerful and stable compound often used in military applications and commercial explosives, and it is effective when used in conjunction with a primary explosive that can provide the necessary energy to trigger its detonation. This distinction is critical in explosive safety and handling protocols, as secondary explosives like RDX are typically safer to store and transport than primary explosives.

In contrast, options such as black powder and ANFO are classified differently; black powder is considered a low explosive and is more sensitive, while ANFO is a mixture that also acts more like a low explosive, as it can deflagrate rather than detonate unless confined. On the other hand, TNT is considered a secondary explosive but is less sensitive compared to RDX; however, the focus on RDX as the chosen answer emphasizes its specific classification within explosives.