Passage Summary: People worry about chemicals hurting the ozone, but a massive star explosion long ago did way more damage and our ancestors were fine, so the chemicals today probably aren't a problem.

Conclusion: There is no reason to believe that chlorofluorocarbons (CFCs) are currently harming humans by damaging the ozone layer.

Reasoning: A supernova in the distant past caused significantly more damage to the ozone layer than CFCs do today, yet it had no major negative impact on our early ancestors.

Analysis: The commentator is using a historical analogy to dismiss a modern concern. To weaken this, we need to find a reason why the comparison doesn't hold up. Perhaps modern humans are biologically more sensitive to radiation than our ancestors were, or perhaps our ancestors had lifestyle habits—like living in caves—that protected them from the ozone damage. Look for an answer that highlights a relevant difference between the supernova event and the current CFC situation that would make the current situation more dangerous.