How have human systems and political systems shaped South America?

How do oceanographers measure the salinity of ocean water?

Name the two rivers that run through the fertile crescent. how were the rivers both positive and negative to societies of the fertile crescent?

Which of the following best describes the purpose of a nation’s boundaries? a. to limit the movement of goods and people b. to make it easier for cartographers to create maps c. to make the movement of goods and people easier d. to prevent other countries from invading territory