Hello. You did not present the answer options, which makes it impossible for your question to be answered accurately. However, I will try to help you in the best possible way.
According to the description of the prefix and suffix of the word "monologue", we can see that a sentence that would well illustrate the meaning of that word would be a sentence that presents an individual who is talking to himself in a logical and conscious way.
The word "monologue," in fact, means "talking to yourself," however, this is a conscious and logical action of the individual who is aware that he is speaking and exposing his thoughts to himself. Thus, we can consider that a sentence that shows an individual talking to himself and exposing his thoughts and emotions in a solitary way, would well illustrate the meaning of "monologue."