The correct answer is A) By doing manual labor that increased the profit of cash crops grown on plantations.
The majority of African slaves helped the colonial American economy by doing manual labor that increased the profit of cash crops grown on plantations.
The slave trade sent slaves from Africa to America where they were sold. Many colonies based its economy on slavery to produce the number of crash crops needed in the southern plantations to be exported to Europe. For instance, tobacco was the most important cash crop in the colony of Jamestown, Virginia. The middle colonies of New Jersey, New York, Pennsylvania, and Delaware successfully grew many crops. They were considered the "breadbasket" of America.