Which of the following best describes the sources a historian uses to support an argument

Assuming that this is referring to the same list of options that was posted before with this question, the correct response would be "primary and secondary sources", since the historian uses secondary sources to give background information on the topic in question, and primary sources to make an original point that adds to the body of research. 

Contributing factors  leading  to the harlem renaissance were the great migration of african americans to northern cities, which concentratedambitious  people in places where they could encourage each  other, and the first world war, which had created new industrial work opportunities for tens of thousands of people.