Answer:
The correct answer is: Ships picked up rice at the port, and brought slaves.
Step-by-step explanation:
In that time rice agriculture was called "the best opportunity for industrial profit which 18th century America afforded." And Charlestown meant one of the most important ports, with the time traders found out that the importing of slaves from the traditional rice-growing were even more profitable because The South Carolina rice planters were willing to pay more for those slaves.