Comets are primarily composed of what type of materials?

Comets are primarily composed of an icy nucleus with dust particles, making this the correct answer. This unique structure allows comets to display their distinctive tails when they approach the Sun. As the comet gets closer, the heat from the Sun causes the ice to sublimate, turning into gas and dust that gets pushed away by the solar wind, forming a glowing coma and a tail that can extend for millions of kilometers.

The icy composition of a comet is often referred to as "dirty ice," consisting mainly of water ice, along with frozen gases like carbon dioxide, ammonia, and methane, mixed with dust and rocky materials. This combination of ices and solid particles is what gives comets their distinctive look and behavior compared to other celestial bodies.

The other options do not accurately describe the primary composition of comets. Metal ores and rocky materials are more characteristic of asteroids or terrestrial planets; gas and dust, while present in a comet's tail, do not encompass the solid core which is crucial to a comet's structure. Thus, the specific mention of an icy nucleus with dust particles perfectly captures the essence of what comets are fundamentally made of.