Final answer:
Neil's most likely rationalization for seeking reimbursement for personal expenses by falsifying other expenses is the belief that no one will ever know about it.
Step-by-step explanation:
In the scenario where Neil sought reimbursement for personal entertainment expenses by falsifying transportation fares and gratuities, the most likely rationalization for Neil's actions is C. No one will ever know about it. This rationalization aligns with the deceptive nature of his actions where he assumes the misrepresentation will go undetected. No higher authority or justification for a greater good is presented that would align with option A, which would claim the action is not illegal, or option B, which would suggest it's in everyone's best interest. There's also no implication that Neil believes his boss will cover for him (option D), nor does the justification seem to fit any different rationale (option E).