Why are erosion and deposition important?

In a repredentive democracy: a.) people come together in large meetings to vote on public policy b.) the people govern themselves c.) political power is held by a small group of people d.) people elect officials to run the government for them

After railroads, the next revolution of transportation came with the development of (a) automobile (b) telegraph (c) steam engine

In africa what do they call a crop grown for direct sale and not for use?