QUESTION TYPE: Strengthen – Exception
CONCLUSION: The depletion of the ozone layer is the primary cause of the declining amphibian population.
REASONING: Ozone blocks UV-B. Amphibians and amphibian eggs are particularly vulnerable to UVB because they lack hair, hide or feathers and their eggs lack leathery or hard shells.
ANALYSIS: The main point is that lack of ozone has been harmful. The wrong answer focuses specifically on UV-B. Lack of ozone does cause harmful UV-B to get through but the argument doesn’t rule out the possibility that ozone has other harmful effects.
- CORRECT. This doesn’t help. If lack of ozone was letting other dangerous things through then the argument would be even stronger.
- This supports the argument by showing that UV-B may be a cause.
- This shows that the proposed cause (ozone depletion) is occurring everywhere amphibians live.
- This rules out habitat loss as an alternative explanation.
- The ozone layer has also been declined continuously. If the amphibian population had an unsteady rate of decline then some other factor might have been the cause.
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