As a Result of Measurements by the Galileo Spacecraft, What

As a result of measurements by the Galileo spacecraft, what is now believed to be the internal structure of Io?

A) a thick mantle of rock over a core of iron and iron sulfide
B) a thick mantle of ice over a core of rock
C) entirely or almost entirely rock, with no evidence of ice or a differentiated metallic core
D) a thick crust of ice over a rocky mantle and a small, possibly molten, iron core