What are comets primarily composed of?

Comets are primarily composed of water, dust, frozen gases, and icy lumps, which aligns perfectly with the characteristics defined in the question. The core of a comet, often referred to as the nucleus, is made up of these materials, giving comets their distinctive structure. As a comet approaches the Sun, the heat causes the ice to sublimate, creating a glowing coma around the nucleus and often forming a tail that points away from the Sun. This fascinating behavior and composition make comets unique celestial bodies in the solar system.

Other options include materials like rocks and metals, which are more characteristic of asteroids rather than comets. Similarly, gas and vapors do not encapsulate the overall solid and icy nature of a comet, while stardust and cosmic rays pertain to different astronomical phenomena. Thus, the selection of water, dust, frozen gases, and icy lumps accurately reflects the composition that defines comets and their behavior as they traverse the solar system.