Final answer:
Jupiter's moons differ widely in composition, with Ganymede and Callisto having a mix of rock and ice. Io is highly volcanic, whereas Europa may have a subsurface ocean. Some outer moons of Jupiter and other planets may be captured asteroids.
Step-by-step explanation:
The moons of Jupiter are diverse in their compositions. Ignoring the crossed-out options and focusing on factual information, Jupiter's largest moons, Ganymede and Callisto, are composed of roughly equal parts ice and rock. On the other hand, Io and Europa are denser and exhibit different properties. Io is the most volcanically active body in the solar system, while Europa is believed to have a subsurface ocean beneath its ice crust. Their compositions and active geological processes contrast significantly with our comparatively dry, rocky Moon.
It's important to note that not all moons of the outer solar system were formed in place; rather, some smaller outer moons could have been captured by the planets' gravity early in the history of the solar system, much like Phobos and Deimos of Mars are believed to be captured asteroids. However, for Jupiter's moons, the current understanding is that they are a mix of both native and potentially captured bodies with varied compositions ranging from rock to ice.