Peaks in immigration to the United States reflect changing circumstances at the global scale. Refer to the graph above to answer the following: Define voluntary migration.
Compare voluntary and forced migration.
Identify an economic motivation for migration.
Explain the factors that contributed to the rapid decline in immigration between 1900–1940.
Compare the demographics of the immigrant population at the peak in 1900 and the peak in 2000.
Explain the economic factors motivating immigrants in the late 20th century.
Describe how chain migrations impact the cultural landscape.

Explanation:

D) The causes aren't shown, but likely it's due to immigration quotas and restrictions set. These were laws aimed to reduce people coming into the country. For instance, the Immigration Act of 1907 was made when population numbers increased dramatically in large cities like New York (and things like crime and unemployment rates went up as well).

E) In the early 1900s, most of the immigration came from Europe. This is shown by the blue portion of the graph. Then by the peak in 2000, the breakdown in immigration demographics is now more diverse due to the various colors shown.

F) Immigrants came looking for better opportunities, better paying wages, higher standards of living, etc. Some fled from brutal dictators and/or war conditions in their home country. Ideally they would have preferred to stay home where they're most comfortable, but these factors were enough to get them to travel vast distances, deal with terrible hardships such as disease, just to have a chance at a better life. The economic factors deal specifically with money of course, but the other factors shouldn't be overlooked as well.

a is the answer i believe.