What are comets primarily composed of?

Comets are primarily composed of ice, dust, and rocky material, which is why the selected answer is the most accurate representation of their composition. Comets originate from the outer regions of the solar system, such as the Kuiper Belt and the Oort Cloud, where they are built from primordial materials. They contain a significant amount of frozen gases, including water ice, carbon dioxide, ammonia, and methane, which makes up the icy nucleus of the comet.

As comets approach the Sun, the heat causes the ices to sublimate, creating the characteristic coma and tails that are typically seen when they are active. The dust and rocky components add to the solidity of the comet's nucleus and give it a diverse structure. This composition is fundamentally different from the other materials mentioned in the other answer choices, which do not accurately reflect the unique characteristics and makeup of comets.