What was the cause of the population decline shown on the chart?

Millions of American Indians died as their resources were exploited by European colonists.
Millions of American Indians migrated to avoid contact with Europeans.
American Indian groups experienced strong population growth after the introduction of European foods.
American Indian populations were decimated by European diseases.

D- they brought diseases

. political or economical policy that isolates a country from participating in international relationships. it has been suggested that the united states participates in isolationism because of its lack of involvement in particular wars or alliances.

answer: secession

secession, as it applies to the outbreak of the american civil war, comprises the series of events that began on december 20, 1860, and extended through june 8 of the next year when eleven states in the lower and upper south severed their ties with the union. the first seven seceding states of the lower south set up a provisional government at montgomery, alabama. after hostilities began at fort sumter in charleston harbor on april 12, 1861, the border states of virginia, arkansas, tennessee, and north carolina joined the new government, which then moved its capital to richmond, virginia. the union was thus divided approximately on geographic lines. twenty-one northern and border states retained the style and title of the united states, while the eleven slave states adopted the nomenclature of the confederate states of america.

explanation: