Correct answer choice is :
C) Sea-floor spreading.
Explanation:
The Earth's magnetic field is believed to be produced by fluid changes in the liquid, outer part of the Earth's core, which is mainly formed of iron. The reversal method is not completely intermittent as it is on the sun, whose fascinating field changes every 11 years. The geologic record shows that numbers of pole cancellations have happened during Earth's history, they happen when pieces of iron atoms in Earth's liquid outer core become reverse-aligned, like tiny electromagnets located in the different direction from those around them.