Final answer:
A flat character is simple and does not undergo significant change, while round characters are complex and dynamic characters are those that experience change. If a character is described as lacking depth and development, the correct term for such a character is flat.
Step-by-step explanation:
The character described as a flat character is one that is typically simple, not very complex, and does not undergo any significant changes throughout the story. According to E.M. Forster, a flat character can often be summarized by a single sentence and is used to represent a specific trait or idea. In contrast, a round character is complex, deep, and undergoes development, often changing in a convincing way in the story. Dynamic characters are those that do experience change, much like round characters. Therefore, if we are to describe a character about whom we know very little and who does not undergo any significant change or development, the correct answer would be c. Flat.