The slow drifting of sections of the earth's crust, sometimes separating, other times colliding, is known as . plate tectonicsb. crust dynamicsc. continental divergenced. continental convergence

a. plate tectonics

Explanation:

plate tectonic  theory describe the fact that the earth is divided into different thick plates(crust) that moves slowly and change in sizes. This plates drift away from each other , slides past another or even collide with each other . The resulting movement of this plates brings about the uneven configuration of the earth crust. Some part of the earth are been subducted while some are uplifted resulting to mountain belts and hills. The plate tectonic idea was born out of the theory of continental drifting and seafloor spreading.

continental drifting talks about the movement of the continents on the earth surface . it is believe that the continents changes position in relation to one another.  Sea floor spreading is the idea that the sea floor drift away from each other  into two parts with the mid oceanic ridge forming the mid points . As you move away from the mid oceanic ridges the floor becomes increasingly older in age.

Generally, plate tectonic plays a major role on how the earth looks, the structures that are formed and the rocks formed.