What is the theory of plate tectonics?
A) A large plume of hot mantle material rising from deep within the Earth.
B) A deep central fracture found along the crest of the mid-ocean ridge.
C) On land, an elongated valley that overlies a region of stretching crust.
D) In geology, the theory that says that the Earth's crust is composed of a mosaic of large, slowly moving plates.
