The correct answer is formal yet conversational.
Explanation: The sentence "Neuroscience tells us why this happens" adopts a tone that is scientific, as it refers to neuroscience. However, the use of "us" makes it sound more informal and engaging, as if the author is having a conversation with the reader. This blend of formal scientific content and conversational language creates an approachable tone that is informative but not overly stiff or technical.