Answer:
B. allowed illiterate citizens to understand the key points of the stories.
Step-by-step explanation:
This is the main advantage of producing illuminated manuscripts in order to spread Christianity. In ancient times, people were not generally able to read and write. This knowledge was limited to a few people who were wealthy or powerful enough to be educated. Therefore, in order to reach less educated people, illustrations were particularly useful, as they allowed people to understand the key points of the stories.