High explosives do not need to be confined in order to?

High explosives are characterized by their ability to undergo detonation, which is a rapid and violent chemical reaction that produces a shock wave. For a substance to be classified as a high explosive, it does not need to be confined in order to initiate a detonation. This is because high explosives can generate sufficient pressure and temperature on their own to propagate the explosive reaction once the initiation threshold is met, either through impact, friction, or a detonating fuse, among other methods.

In contrast, confinement is often a factor for other types of explosives, such as low explosives, which require confinement to enhance the rate of combustion and increase their effectiveness. The other choices involve different characteristics of explosives: burning refers to the slow combustion associated with other explosives, producing shrapnel typically occurs when high explosives are confined and then ruptured, and safe transport often requires careful handling and confinement to prevent accidental detonation. Thus, the ability to cause a detonation independently of confinement is a defining feature of high explosives.