Question

according to the theory proposed by harry hess, what causes continents to move?
continental drift
magnetic polarity
seafloor spreading
deep - ocean trenches

Explanation:

Harry Hess proposed the theory of seafloor spreading. Seafloor spreading is the process by which new oceanic crust is formed at mid - ocean ridges and causes the movement of continents as part of the plate tectonics process. Continental drift is an older concept. Magnetic polarity is related to the Earth's magnetic field and not the direct cause of continental movement in Hess's theory. Deep - ocean trenches are features related to subduction zones, not the cause of continental movement as per Hess's theory.

Answer:

C. seafloor spreading