Which of the following best defines an explosive device?

The best definition of an explosive device is one that is designed specifically to cause physical harm by means of an explosion. This definition encompasses the core function of such devices, which is to utilize explosive materials to generate a rapid increase in pressure and temperature, leading to an explosion that can produce destructive effects.

Options that specify the intended damage (such as only causing fire damage) or limitations on how the device can detonate (like requiring remote control) do not capture the broader range of explosive devices or their purposes. Similarly, while some explosive devices may utilize chemical reactions, this would not fully define all types of explosive devices, as not all explosions are caused by chemical reactions alone. Thus, the emphasis on the intentional causing of physical harm through an explosion fully encapsulates what an explosive device is meant to do.