Answer;
C. seafloor spreading
Step-by-step explanation;
The theory of seafloor spreading states that new ocean crust is continually being formed, and that this crust is slowly carried away from its point of origin over a period of time.
Paleomagnetism helped explain an unusual observation from the 1950s. Magnetic studies revealed that the ocean floor was comprised of parallel bands of crust having alternating magnetic polarity.These magnetic bands were symmetric about the mid-oceanic ridge.