The correct answer in - B. Conflict often resulted in a higher number of slaves for trade.
Whenever there was a conflict within Africa, it meant that there are going to be more slaves on the market. This was due to the tradition of the African tribes to capture enemies and keep them as slaves, and also the already developed network of selling slaves to the Europeans. After every conflict, the winning side had lots of slaves, and Europeans rushed to get their hands on the best ones, so the African tribes that were selling them were making a nice profit, while the Europeans were getting excellent labor force.