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

D. is a gravity-driven downslope movement of natural materials.

Explanation:

The mass wasting is defined as the slope movement or the downward movement of the debris or the rock wastes down the hill by the action of the geomorphic process like the soil, the sand and the regolith and may be continuous or discontinuous associated with the flow of the debris, mud and the rock slide or the flow. Based on the rock these are classified as  Creep: which is long term movement and is a combination of the soil or the rocks, the steeper the slopes the faster is the fall. Landslides are associated with landslips and thus are more rapid and hence cause more destruction as the flow of material occurs along with the action of the gravity. They also include lahar and the earth flows.

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