The Magnetic Field of Earth in the Geologic Past Is

Multiple Choice

The magnetic field of Earth in the geologic past is ____________.

A) unknown,but it is assumed to have been identical to today's
B) known to have been constant through geologic time,due to remnant magnetization of iron-rich minerals in rocks
C) known to have experienced numerous polarity reversals,due to remnant magnetization of iron-rich minerals in rocks
D) known to have been constant through time,on the basis of theoretical calculations