D. They had more job opportunities there.
Step-by-step explanation:
Many former slaves would migrate to cities because there were many more job opportunities there.
After obtaining freedom, many former slaves would travel to live up in the Northern states. Not only were the Northern states more accepting of African Americans, there were also many more job opportunities for them to obtain.
The Northern states focused on industrialization, unlike the Southern states who focused on agriculture. This meant that there were starting to be factories, which were in dire need of manpower in order to produce and make items. This meant that many African Americans would obtain factory jobs, as there was an abundance of them open.