Poetry tells a story and expresses emotion in a way that is concise, emotionally charged, and musical. There are different types like a narrative and lyric. A narative tells a story, which has a plot and characters. A lyric poem is more about feelings and emotions. The speaker is the character.
C is the answer you are looking for. A common idea isn't a moral, the generalization is the Main Idea, but not quite the moral. The thought of the characters almost never have the moral in them. Therefore, C is your answer.
C. motherhood you could have just use the process of elimination