The Presence of a Magnetic Field Is a Good Indication

The presence of a magnetic field is a good indication that

A) the Earth's interior must be completely molten to the center.
B) the Earth's interior has had time to solidify, with a rigid bar magnet created.
C) the Earth's interior is similar to Mercury's, as both have fields.
D) a huge iron meteorite lies somewhere high up in the mantle, not in the core.
E) the Earth has a liquid metal outer core, spinning rapidly as it rotates.