The best answer here is B. While Achebe does explore variations of each of these answers (except for C as the missionaries were white), B is the best answer because he slowly introduces the culture of the White man into the culture of his story.
The Igbo culture was one that was still firmly entrenched in the ways of its ancestors. The people still did things they way they were done years before. It was important for them to continue to do this because it brought them closer together as a people. However, with the introduction of the White missionaries, things begin to change.
People no longer honor their ancestors as they once did. They do not observe rituals or various things the way they once did. This is difficult for Okonkwo especially since he still firmly believes in the way things were done. The White missionaries coming to the Igbo shows the creeping effects of colonialism in a place like Africa.
It shows how the missionaries helped to change not only the culture, but the people with the introduction of not only their religion but also some of their things, such as the bicycle and other goods. By the end of the novel, we have a fairly good idea that the Igbo culture as it was presented at the start of the book will be no more because the missionaries have taken the individuality they had in their culture and turned them away from it.
