Mass movement
a. happens only when the slope of a hill gets steeper than the angle of repose.
b. can't happen underwater because the buoyancy force of water is too great.
c. is more likely to happen under dry conditions than under wet conditions.
d. is a gravity-driven downslope movement of natural materials.

The correct answer is option D. is a gravity-driven downslope movement of natural materials.

Explanation:

Mass movement or Mass wasting is the process by which natural materials such as soil, soil, sand, regolith, and rocks move downward in the form of a solid mass under the force of gravity. The characteristics of this process are similar to those of the mud flow or the debris flow.

Mass movement can occur very slowly, especially in dry areas or with a lot of rain so that the surface has been stabilized by vegetation.

Sometimes it can happen quickly, where the material that slides are rocks or earth and its consequences can be disastrous.

brave new world, aldous huxley (1932)