Correct Answer:
A. Mercury
Mercury is the correct answer because it is one of the two planets in our solar system that do not possess any natural moons. Its proximity to the Sun and relatively small gravitational field contribute to this characteristic, making it unable to retain a satellite. Venus also lacks moons, making it another planet without natural satellites; however, Mercury is the designated correct option here. Mars, conversely, has two small moons named Phobos and Deimos. Saturn is renowned for its extensive system of numerous moons, including the large moon Titan, making this option incorrect. Understanding planetary characteristics helps differentiate these celestial bodies.