ANS:D - gravitational force.

Alluvial- running water.
Lacustrine-still water (lake).
Marine- sea water.
Aeoline-wind.
Loess-wind.
Tuff-wind.
Glacial- ice.
Colluvial/talus-gravity.
Marl-dead aquatic life.
Peat- organic material.
Loam- an equal mix of clay silt organic material.
Bentonite-volcanic ash.
Laterite- leaching of silica.
Gumbo- highly sticky plastic soil.