The Dynamo Theory Holds That

Multiple Choice

The Dynamo Theory holds that:

A) lightning plays a major role in generating our magnetic fields.
B) any other planet of similar density will also have a strong magnetic field.
C) the Earth's core, like Mercury's, is now a solid, rigid bar magnet.
D) magnetic fields are generated by rapidly spinning, fluid magnetic interiors.
E) the Earth's magnetic field must switch polarities every few million years.