Based on the information provided in this excerpt, I would say that Tom is hard-working but he lacked interest in what he's doing because he's not making an effort to understand it. Thank you for posting your question. I hope that this answer helped you. Let me know if you need more help.
The answer is A, because the protagonist is the main character, and that's what Rider is. The other answers don't really make sense in terms of the role he plays in the story.
Hope I helped!
