The process of laying down materials, such as rocks

Erosion

Explanation:

Erosion is the geological process in which earthen materials are worn away and transported by natural forces such as wind or water. A similar process, weathering, breaks down or dissolves rock, but does not involve movement.

i assume that's what you mean by "laying down materials, such as rocks."

according to classical republican political theory, which democratic republics would function best?

a.   small republics, with people who had similar interests

b.   large republics, with people who had competing interests

c.   republics made up entirely of landowners

d.   republics made up entirely of servants