Earth Has an Average Density of 5500 Kg/m³, Although the Density

Multiple Choice

Earth has an average density of 5500 kg/m³, although the density of rock on its surface is about 3000 kg/m³. What conclusion can be reached about Earth's core from this observation?

A) Earth's core consists of lower density material than surface rock.
B) Earth's liquid core has a low density, so it must have a far higher density at moderate depth.
C) Earth's core must be very hot.
D) Earth's core is made of material far denser than surface rock.