Areason why slavery developed in the american colonies was indentured servants became enslaved after seven years. southern plantation owners needed more labor at lower costs. indentured servants no longer wanted to come to the colonies. new england farmers needed with harvesting cash crops..

Although forced labour started with the system of indentured servitude, at the end of a established period the servants would become free men and own land. Slavery developed in the American Colonies because of the expansion of  plantations that produced goods such as cotton or tobacco.  Plantations were large and they needed a lot more workers than small farms in order to produce that is the reason why their owners started buying human beings as a captive work force in order to meet those requirements.

Southern plantation owners needed more labor at lower costs.

letter d is correct.

these acts divided the south into five military districts.