What does the phrase 'water-rich icy body' imply about 'Oumuamua's composition?

• A. It contains metallic iron.
• B. It contains water ice and entrapped volatiles.
• C. It is a rocky asteroid with no ice.
• D. It is composed mainly of carbon nanotubes.

Answer: (B)

The phrase points to a body where water ice is a major component and where volatile gases are trapped within that ice. “Water-rich” signals abundant water ice, and “icy” reinforces that the material isn’t dry rock or metal. The idea of entrapped volatiles means other gases (like CO, CO2, methane, ammonia, etc.) are held inside the ice matrix or pores and could be released if the body warms. This kind of composition is typical of comets or icy bodies formed far from the sun, not of a rocky asteroid with no ice or a metal-rich object. So, the most fitting implication is that it contains water ice and other volatiles.