Which of the following describes an asteroid?

An asteroid is defined as a small rock body that orbits the Sun, primarily found in the asteroid belt, which is located between the orbits of Mars and Jupiter. These objects are remnants from the early solar system, composed mainly of rock and metal, and range in size from a few meters to hundreds of kilometers in diameter. The distinction of asteroids from planets is that they do not have sufficient mass to be rounded by their own gravity and also do not clear their orbit of other debris.

This definition aligns precisely with the characteristics of an asteroid, making it the correct choice. The other options refer to different celestial bodies or concepts that do not match the definition of an asteroid. A planet, for example, would be much larger and have the ability to clear its orbital path, while a star is a massive body undergoing nuclear fusion and a gaseous celestial object doesn't share the solid composition and orbital characteristics typical of asteroids.