The correct option is: GRATINIC ROCK IN THE OCEAN FLOOR. Sea floor spreading refers to the process by which molten materials add new oceanic crust to the ocean floor. This process occurs slowly across the earth's middle ocean ridges. Harry Hess formulated an hypothesis to explain the phenomenon of sea floor spreading and all the above options support his hypothesis with the exception of option C.
Having on valence electron indicates that these elements are on the same column/group of the periodic table. Both these elements will bond with a -1 charge.
