Final answer:
The rise of Memphis as the Cotton Capital of the South was significantly aided by it having a large inland port on the Mississippi River which was pivotal for transportation and trade.
Step-by-step explanation:
The factor that best completes the list of those contributing to the rise of Memphis as the Cotton Capital of the South is the Large inland port on the bank of the Mississippi River. Memphis's central location made it a focal point for commerce, and its fertile land was ideal for cotton cultivation. The presence of a large inland port on the Mississippi River facilitated the movement of cotton and other goods, allowing for ease in transportation and trade, which are crucial for a region's economic prosperity.