Final answer:
The main idea is that Ibn Battuta admires the West African Muslim's religious commitment but disapproves of their social customs concerning women's behavior, which is best represented by option B.
Step-by-step explanation:
The main idea of the passage from Ibn Battuta's diary, which captures his observations during his visit to West Africa in 1349-1350 CE, is best represented by option B, which states: Ibn Battuta admires the West Africans for their commitment to Islam but does not approve of how their women behave.
While Ibn Battuta discusses the religious zeal of the Muslim community in regard to prayer and learning the Koran, he contrasts this with his surprise and disapproval of the social customs related to women's behavior, particularly their interactions with men and lack of modesty as he understood it. Thus, Ibn Battuta offers a complex view that acknowledges the piety of West African Muslims while criticizing aspects of their cultural practices that deviate from his expectations.