Why was slavery profitable in the south?

slaves were better factory workers.
farmers received a higher price for crops grown by slaves.
the cotton gin made it profitable.

Id say C but in reality it was more profitable because farmers had to pay slaves next to nothing if not anything and could have multiple workers in poor conditions so mass amounts of free workers saved them money and they could work them 24 hours a day until they dropped making the process go faster producing more than other competing farms. A sad truth from our past.. hope this helps! 

Why do you have to ask such hard questions.