What Conditions Are Considered to Be Necessary for a Planet

Multiple Choice

What conditions are considered to be necessary for a planet to be able to generate an intense magnetic field?

A) ionized and electrically conducting layer in its atmosphere
B) electrically conducting material in its interior and slow rotation because rapid rotation will destroy a magnetic field
C) solid iron core into which a magnetic field was induced early in the planet's history
D) relatively rapid rotation and electrically conducting material in its interior