Which description best fits a comet?

• A. Objects made up of dust and ice that travel through space, with tails near the Sun.
• B. A small, rocky fragment orbiting a planet.
• C. A telescope used to observe distant galaxies.
• D. A device that relays signals from deep space.

Answer: (A)

Comets are icy bodies that travel through space and become visible as they approach the Sun. When heat from the Sun warms the comet, the ice sublimates into gas and dust, creating a glowing coma around the nucleus. The solar wind and radiation push this material away, forming a tail that points away from the Sun. This combination of dusty ice and a Sun-driven tail is what makes comets distinctive, and why the description that mentions dust and ice with tails near the Sun is the best fit.

That helps differentiate from other objects: a small rocky fragment orbiting a planet would be more like an asteroid; a telescope is an instrument for observing distant objects; and a device that relays signals from deep space describes a communicator or antenna.