Magnetic reversals have to support

Magnetic reversals have helped support the theory of sea floor spreading, that Harry Hess, professor of geology had put forth. He proposed that the ocean progressively widens as new sea floor is created along a crack that follows the crest of ridges found in the middle of the ocean.

In 1963, Fred Vine, Drummond Mathews and others found that the crust surrounding the mid-ocean ridges showed alternating bands, each band magnetized with a polarity opposite the surrounding bands. They suggested that as new sea-floor crust was formed around the crack or rift in the mid-ocean ridge, it magnetized differently depending upon the polarity of the planet at that time, supporting the theory of Harry Hess.  

d.7.5cm is your answer

i think the answer would be b