Final answer:
Sub-Saharan Africa would fit best in Wallerstein's Periphery, which refers to less developed countries that are exploited for their resources. Additionally, West Africa was the region most involved in the Trans-Atlantic slave trade.
Step-by-step explanation:
To answer the question about which region would fit best in Wallerstein's Periphery, we must understand that Immanuel Wallerstein's World-Systems Theory divides the world into Core, Semi-Periphery, and Periphery countries. The Periphery countries are typically less developed and are exploited by Core countries for their raw materials and cheap labor. Considering the development status and global economic contributions of the regions provided in the question, Sub-Saharan Africa (option D) would fit best in Wallerstein's Periphery.
The region of Africa most directly involved in the Trans-Atlantic slave trade was West Africa (option b). This area was heavily affected due to its role as a center of a cruel and inhumane trade system that transported millions of enslaved African people to the Americas.