What was John C Calhoun‘s position on slavery

What is on reason why areas that are just beginning to industrialize typically have a higher rate of population growth than countries that are already industrialized

Which events are correlated but do not necessarily have a causal relationship?

Which source would best a historian understand the effect of the great chicago fire on families? a. a biography of a chicago family displaced by the fire b. a letter from a grandmother in new york to her family in chicago c. a newspaper editorial about families who were displaced d. an oral history dictated by an adolescent who fled the fire