Final answer:
The article detail that supports the opinion on developing resilience is the one highlighting scientific research on the brain's adaptability to grow stronger after challenges.
Step-by-step explanation:
The detail from the article that best supports Megan Gunnar's opinion that people can develop resilience after facing hardships is the one stating that scientific research shows how the brain can adapt and grow stronger after experiencing challenges. This detail provides a factual basis for the claim of developing resilience, demonstrating an understanding of the neuroscientific underpinnings. It aligns closely with the theory that hardships can lead to personal growth and increased resilience.