Passage Summary: More people are using sunscreen than ever before, yet skin cancer rates are still going up, so the author thinks sunscreen doesn't actually work.

Conclusion: Using sunscreen is probably not an effective way for an individual to lower their risk of skin cancer.

Reasoning: Over the last quarter-century, skin cancer rates have risen even though the use of sunscreen has become much more common.

Analysis: This argument suffers from a classic failure to consider alternative explanations for a trend. It assumes that because the overall rate is up, the preventative measure is failing, ignoring the possibility that rates would be even higher without it. To weaken the argument, look for an answer that suggests other factors—like people spending more total time in the sun because they feel 'safe'—are responsible for the increase.