Which action is an example or direct democracy

Use the following map to answer the question below: what key role did the location of the tigris and the euphrates river play on the development of mesopotamia? a.) mesopotamia was settled between the two rivers to take advantage of the natural barrier produced by the arabian desert. b.) mesopotamia was settled between the two rivers to take advantage of the protection provided by the rivers. c.) mesopotamia was settled between the two rivers to take advantage of the fertile soil produced by floods. d.) mesopotamia was settled between the two rivers to take advantage of the drinking water provided by the persian gulf.