The Structure of Callisto, the Outer Galilean Satellite of Jupiter

Multiple Choice

The structure of Callisto, the outer Galilean satellite of Jupiter, is thought to be

A) a mixed ice-rock interior surrounded by a liquid ocean and then a solid icy crust.
B) mostly or entirely rock, with no firm evidence of an iron core, and active volcanoes on its surface.
C) an iron core surrounded by a rocky mantle and an ice mantle and crust.
D) almost all water ice, in view of its low average density.