What describes the composition of a comet in pyrotechnics?

The composition of a comet in pyrotechnics is accurately described as a pellet of pyrotechnic composition. Comets are specifically designed to create a visual effect in fireworks displays, often characterized by their tail-like appearance as they emit sparks and colored flames.

The term "comet" typically refers to a particular type of firework that utilizes a solid mass of pyrotechnic material, which is formulated to produce a sustained burning effect. This composition usually includes individual components such as oxidizers, fuels, and colorants that work together to create the desired visual effects when ignited.

The other options do not accurately reflect the nature of a comet. A comet is not a liquid form of explosive material, as its primary composition is solid and specific to pyrotechnic formulations. It is also not solely made of black powder, which is just one component type and does not constitute the entire pellet composition. Lastly, it is not a solid block of compressed gas, as that would not provide the necessary combustion characteristics for the visual performance expected from a comet in fireworks.