Here are the answers to your questions:
Question 1: Approximately what percentage of African Americans lived in the South at the start of World War I?
Answer: C 70%
Question 2: What event seemed to start the Great Migration?
Answer: B World War I
Question 3: What event seemed to cause the Great Migration to slow?
Answer: D the Great Depression
If you have any more questions or need further assistance, feel free to ask!