Which compelling piece of evidence supported the theory of seafloor spreading?

Which compelling piece of evidence supported the theory of seafloor spreading?


W) The discovery and mapping of magnetic stripes on the seafloor
X) The discovery of deep earthquakes along the Pacific Rim by Charles Richter
Y) The recordings of submarine volcanic activity along mid-ocean ridges in the 1970s
Z) Sir Edward Bullard's geographic fit of the continents


Answer: W