What is the primary evidence that forms the basis of seafloor spreading? A. The rocks on the mid-oceanic ridges change densities in a symmetrical manner. B. The magnetic properties of rocks along the mid-oceanic ridges change alignment in a symmetrical manner. C. The rocks along the mid-oceanic ridges show age patterns in a symmetrical manner. D. The rocks along the mid-oceanic ridges have mineral patterns in a symmetrical manner.