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What is the main feature of a comet?

  1. A small and rocky object orbiting a planet

  2. A large ball of gas found in a galaxy

  3. A small and icy object that orbits a star

  4. A cloud of gas and dust in space

The correct answer is: A small and icy object that orbits a star

The main feature of a comet is that it is a small and icy object that orbits a star. Comets are composed primarily of ice, dust, and other organic materials. When they approach the sun, the heat causes the ice to vaporize, creating a glowing coma and often a spectacular tail that can stretch millions of kilometers. This tail always points away from the sun due to the solar wind, giving comets their distinct appearance. In contrast to the other options, a comet's icy composition and its behavior when near the sun set it apart from objects like asteroids, which are typically small and rocky and orbit the sun primarily in the asteroid belt. Additionally, while gas giants are indeed large and gaseous, they do not describe the characteristics of comets. Lastly, a cloud of gas and dust refers to nebulae or the components of star formation rather than the specific attributes of a comet. Thus, option C accurately captures the essence of what defines a comet in the context of celestial objects.