Answer : option B) Gravity acting on the edges of plates and friction between the plate and the asthenosphere.
Explanation : The gravitational force acting on the edges of the tectonic plates raise a friction between the plate and the asthenosphere, which results into the motion of the tectonic plates.
Usually, the tectonic plates are found to move because of the intense heat produced from the Earth's core which causes the molten rock in the mantle layer to move and make a motion. It moves in a pattern which is called as convection cell that forms when the warm material rises, and cools, later eventually sink down producing the motion in the tectonic plates.
