What is a meteoroid?

A meteoroid is defined as a small solid body that is traveling through space, particularly one that is significantly smaller than an asteroid. The correct choice highlights that a meteoroid is a clump of dust or rock that orbits the Sun. It is important to understand that meteoroids can vary in size from small grains to objects up to a meter in diameter, and they primarily originate from comets or asteroids.

In contrast, while the first choice refers to a "small rocky body," it may imply a broader and less precise definition than simply characterizing it as a clump of dust or rock. The third option describes a meteor, which refers specifically to a meteoroid that has entered the Earth's atmosphere and is ablaze, often seen as a shooting star. The fourth choice focuses on very small dust-sized particles, which, although they can be classified as meteoroids, does not encompass the broader range suggested in the correct answer. Thus, the characterization of a meteoroid as a clump of dust or rock effectively conveys its properties and origin in the context of space.