"How dumb can you get!" said Robert. "A colossal waste of time if you ask me. So get going! Scram! Shoo!"
Explanation:
According to a different source, these are the options that come with this question:
“You sound as though you never went to school. Or maybe you are a teacher yourself?”
"How dumb can you get!" said Robert. "A colossal waste of time if you ask me. So get going! Scram! Shoo!"
"I'm sorry," Robert said meekly, though the whole thing was getting weirder and weirder.
"It's just that all those ones give me a headache. They actually make things more complicated than they are."
This is the quote that best describes how the dynamic between the number devil and Robert develops throughout the story. In this sentence, we see that Robert opposes the character and wishes of the devil. While the devil wants to help Robert, and considers himself quite intelligent, Robert keeps reminding him of the fact that he is "dumb" and that Robert does not want his help. Therefore, we learn that one purpose of Robert's character is to oppose the number devil.
I saw no man use you at his pleasure. If I had, my weapon should quickly have been out, I warrant you. I dare draw as soon as another man if I see occasion in a good quarrel and the law on my side.
