Final answer:
During the rule of the Mali Kingdom, Islam was first introduced into West Africa.
Step-by-step explanation:
The correct answer is b) Mali.
During the rule of the Mali Kingdom, Islam was first introduced into West Africa. The kingdom, founded by Sundiata Keita in the 13th century, experienced a significant Islamization process under subsequent rulers. The adoption of Islam by the rulers of Mali made it the largest Islamic kingdom in West Africa and led to the establishment of mosques and schools, such as those in Timbuktu, which became centers of Islamic scholarship and learning.