45. Of the following, which is most likely to be composed primarily of ice?
Answer: C
A comet is most likely to be composed primarily of ice.
Comets are often referred to as "dirty snowballs" because they consist mainly of ice, dust, and rocky material. When they approach the Sun, the heat causes the ice to vaporize, creating a glowing coma and sometimes a tail.
A) An asteroid
Asteroids are primarily composed of rock and metal, with little to no ice present. They are found mainly in the asteroid belt between Mars and Jupiter, and their composition differs significantly from that of comets.
B) A red dwarf
A red dwarf is a type of star, not a solid body composed of ice. While stars may have ice in their surrounding planetary systems, the star itself is primarily composed of hydrogen and helium and does not contain ice as a significant component.
C) A comet
Comets are indeed composed primarily of ice along with dust and rocky material. The considerable amount of frozen gas, such as water, carbon dioxide, and ammonia, makes them distinct from other celestial bodies, confirming that this option is correct.
D) The planet Mercury
Mercury is a rocky planet with a thin atmosphere and is not composed of ice. Its surface temperatures are extremely high during the day, making it unlikely for ice to exist on its surface, apart from some permanently shadowed craters at the poles.
Conclusion
C is the correct answer as comets are uniquely characterized by their icy composition, unlike asteroids, red dwarfs, and Mercury, which lack significant amounts of ice. The other options fail to meet the criteria of being primarily composed of ice, reinforcing that comets are the only celestial bodies among the choices that fit this description.