Io Is Believed to Be Mostly Rock and Iron, Much

Io is believed to be mostly rock and iron, much like Earth. How does its density compare to Earth's density?

A) With the same basic composition, its density must be similar to Earth's.
B) Io's density is smaller because it has a mantle of sulfur that is not very dense.
C) Io's density is greater because at its greater distance from the Sun its materials are colder and thus more dense than similar materials on Earth.
D) Earth's density is larger because it experiences more gravitational compression, and the same materials at Earth's core have a greater density than they would at Io's core.