Commentator: Many people argue that

Answer choices

1. A

   Out of Scope: frequency of occurrence2% picked this

   Extraterrestrial influences on the ozone layer tend to occur less often

   We don't care how frequently supernovae damage the ozone layer. The author isn't claiming they occur a lot. She's just claiming that if THAT didn't do ultraviolet related harm, then how could today's chlorofluorocarbon problem do harm.

   2%
2. B

   Not a Difference2% picked this

   Natural events, such as the eruption of volcanoes, continue to damage the

   The "continue to" damage the ozone layer today indicates that this is not necessarily anything different between the two situations. If we had said, "300,000 years ago, there was very little volcanism, whereas nowadays volcanism has depleted the ozone layer to a very vulnerable state", then THAT would be pointing out a meaningful difference that would allow us to say that the less-impactful effect of chlorofluorocarbon (compared to the supernova) could still lead to harm.

   2%
3. C

   Correct83% picked this

   Our earliest ancestors possessed genetic characteristics making them more resistant than we are to the harmful

   Why this is right

   This provides a meaningful difference. Yes, the supernova did more ozone damage than chlorofluorocarbons are doing. And yes the old humans were just fine. But ... they had special genetic resistance to ultraviolet radiation that we don't have. Since we are nowadays more vulnerable to the harmful effects of ultraviolet radiation, it's possible that this less severe damage from chlorofluorocarbons could still end up harming modern humans.

   Skill tested: Weaken · how this choice captures the argument's function is the move to repeat next time.

   83%
4. D

   Not a Difference / Mildly Strengthens3% picked this

   The ozone layer regenerates at a slow rate, barring

   This would be true in both situations, and this doesn't give us a way to argue that modern chlorofluorocarbon damage, which is less severe than ancient supernova damage, is more likely to harm humans. It's possible someone was thinking, "Maybe the supernova's damage and the chlorofluorocarbon's damage is cumulative. i.e., the punches landed in Round 1 were harder than the punches landed in Round 10, but because the boxer was so weakened by Round 10, a weaker punch could still knock them out." If so, this answer would actually work against that type of objection, by saying that the ozone layer regenerates its strength, so whatever damage the supernova did 300,000 years ago would probably have been erased by now, as the ozone layer slowly regenerated.

   3%
5. E

   Unclear Impact10% picked this

   Scientists have discovered that genetic changes occurred in our ancestors during the period in which

   This is similar to our correct answer, except this answer gives us no specific sense in which humans genetically changed. Did they change in a way that made them more / less resistant to ultraviolet radiation? Did they change genetically in some way that suggests that the ultraviolet radiation following the supernova harmed them? We don't know and this doesn't say, so it has no clear impact.

   10%