What is the primary distinction between a comet and an asteroid?

The primary distinction between a comet and an asteroid lies in their composition. Comets are primarily composed of ice, dust, and rocky material, which gives them a characteristic tail when they approach the sun. The heat from the sun causes the ice to vaporize, releasing gas and dust and forming a glowing coma and tail. In contrast, asteroids are made mostly of metals and rocky substances, lacking the icy components that define comets. This compositional difference is significant because it influences the physical appearance and behavior of these celestial bodies as they travel through the solar system.

The other options, while they may describe some aspects of comets and asteroids, do not capture the fundamental difference between the two. For example, size can vary widely among both comets and asteroids, and their orbits can also overlap depending on their individual paths through the solar system. Distance from the sun might influence their visibility or temperature but does not fundamentally differentiate their nature. Thus, the distinction based on composition is key to understanding their differences.