To increase the supply of food, some neolithic communites living in arid regions of the world developed??

Irrigation Systems

Explanation: Irrigation Systems were used to increase the supply of food and water.

i think the answer is c, rivers.

explanation:

sometimes, borders fall along natural boundaries like rivers or mountain ranges. for example, the boundary between france and spain follows the crest of the pyrenees mountains. for part of its length, the boundary between the united states and mexico follows a river called the rio grande. the borders of four countries divide africa’s lake chad: niger, chad, cameroon, and nigeria.

norsemen from northern countries had made earlier journeys