The answer is C. As new colonists and explorers discovered the Americas, they also brought disease. This heavily impacted the American Indians as a majority of their population suffered from epidemics.
"c. A narrative source" is what a historian would use to get a firsthand account of a past event, since in these sources (which are also primary sources) a person is giving a first-hand account of the event itself.
D all 3 of them would be causes
Missouri Compromise is your answer.
