Io's Composition Is Believed to Be Similar to That of the Terrestrial

Multiple Choice

Io's composition is believed to be similar to that of the terrestrial planets rather than to that of the giant planets, yet its density is intermediate between these two groups. Explain.

A) Like the Earth-Moon system, Io is believed to have formed from part of the mantle of Jupiter and thus has a density different from Jupiter as a whole.
B) The intense cold at Io's distance from the Sun compresses its materials and increases its density.
C) The internal heat caused by its gravitational interaction with Jupiter causes Io to expand and decreases its density.
D) Io's smaller mass causes its materials to be compressed less by its own gravity compared, for example, to Earth.