Reversals of the Earth's Magnetic Polarity

Multiple Choice

Reversals of the earth's magnetic polarity

A) occur with a regular periodicity; the next one will happen in about 140 years.
B) have occurred randomly in the past and represent times when the south magnetic pole was swapped in location with the north magnetic pole.
C) have occurred randomly in the past and represent times when the earth turned upside-down
D) are a consequence of major earthquakes.
E) have not happened since the end of the Paleozoic.