What is the term for a small planetary body that orbits a planet?

The correct answer is "moon." A moon, also known as a natural satellite, is a smaller celestial body that orbits a planet. Most planets in our solar system have moons, and they can vary greatly in size and composition. Moons are distinct from artificial satellites, which are human-made objects placed into orbit around a planet.

In the context of the options provided, even though both "satellite" and "moon" relate to orbiting bodies, "satellite" is a broader term that includes both natural and artificial objects orbiting a planet. The term "asteroid" refers to small rocky bodies primarily found in the asteroid belt between Mars and Jupiter, and "comet" refers to icy bodies that release gas and dust, forming a glowing coma and sometimes a tail when they approach the sun. Therefore, "moon" is the most specific term for a small planetary body that directly orbits a planet.