Read this excerpt from infinite jest.

i cannot make myself understood. ‘i am not just a jock,’ i say slowly. distinctly. ‘my transcript for the last year might have been dickied a bit, maybe, but that was to get me over a rough spot. the grades prior to that are de moi.’ my eyes are closed; the room is silent.

how does the narration affect the narrator’s credibility in this excerpt?
his honesty renders him earnest and genuine.
his slang makes him seem youthful and intriguing.
his french jargon makes him seem international.
his explanations depict him as a bit defensive.