Answer:
D. All of the above.
Explanation:
All the above listed reasons are causes of the population shift from South America to the United States.
A is a reason because South America has a long history of dictatorships and authoritarian governments that have committed countless human rights abuses.
B is a reason because South American countries are way poorer than the United States, and as a result, they are less modern.
C is a reason for the same cause as above: the income disparities between the U.S. and South America are so large that a South American working in the United States can easily help support his family back in South America.
