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

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 core must be composed of material with density several times that of the surface material.
C) Earth's core must be very hot.
D) Earth's core is made of material far denser than surface rock.