Why did cotton "rule" the deep south? a. cotton was hard to farm and the slave owners wanted to torment their slaves
b. that was all they could grow
C. it had a high potential for profit
d. all of these

C. It had a high potential for profit.

Explanation:

The Southern States relied heavily on the slaves for their work be it agricultural produce or even farm work. Plantations of tobacco, cotton, grapes, rice, etc. would become the home for many slaves.

The fact that cotton came to 'rule' the deep South was because of the crop's potential to incur a higher profit for the farmer. Depending on the season and market, cotton crops would make huge profits which became a boon for the plantation farm owners. Producing cotton through the slaves enabled the landowners to get a better income than planting other crops. Moreover, it was also relatively easy to grow, be it in large farms or small areas. So, cotton would become the better choice to plant in the plantation farms.  

Thus, the correct answer is option C.

i would go with the last one