Which of the following best explains the change in the number of enslaved persons brought to mainland North America between 1651 and 1750?

A. Growing populations in North Africa that increased the number of people targeted for abduction
B. Increasingly competitive practices in trafficking of people among the British, Dutch, and French
C. Advancements in shipbuilding that facilitated navigation of trade vessels along the African coasts and the Atlantic Ocean
D. A shift from trade in less labor-intensive crops like indigo and cassava to more labor-intensive crops like sugar and cotton