The correct answer is formal yet conversational.
The passage discusses the scientific basis of olfactory remembrance in a manner that is accessible and relatable, while still maintaining a level of seriousness appropriate for a discussion of neuroscience. The use of "Neuroscience tells us why this happens" indicates a formal acknowledgment of scientific understanding, but the overall tone remains conversational as the author shares a personal anecdote that invites the reader to connect emotionally with the experience.