Answer:
b. plate tectonics
Explanation:
Plate tectonics is a theory originated from continental drift and ocean floor expansion. It was developed in 1960, and has become the most accepted among geographers and oceanographers.
According to this theory, the lithosphere moves over the asthenosphere. The lithosphere, in turn, is divided by plates (called tectonic plates) and they slide because of convection currents within the Earth. The heat that comes from the core of the earth warms the mantle and makes the warmer parts rise. These parts cool and fall back down. It is these currents that slowly move the plates that form the earth's crust.
