Here are the answers to your questions:
Question 1: Sectionalism, the Civil War, and __________ prevented the United States from becoming involved in acquiring overseas territories during the mid-1800s.
Answer: C the Gilded Age
Question 2: Which conflict allowed the U.S. to gain control of Puerto Rico, Guam, and other territories?
Answer: C Spanish American War
Question 3: The justification that the U.S. used to become involved in Haiti in 1915 was the Roosevelt Corollary to __________.
Answer: D the Monroe Doctrine