Answer:
C. nucleus of dust, rocks, and ice; may have a long, gaseous trail
B. nucleus is a gas ball; usually come from far away from the sun
Step-by-step explanation:
A comet is a solar mass, composed of dusts rock and ice, and may contain a long tail formed when they come close to the sun. The long tail is usually due to the sun heating up the icy nucleus, and the solar wind blowing the tail away from the sun. Comets are usually formed and found far away from the sun beyond the planet Neptune.
Other celestial bodies are mostly made of rocks and metals, making them a potential good source of industrial raw material. They are usually found closer to the sun, between Mars and Jupiter, and they contain no gas tail.