Passage Summary: A scientist says we shouldn't blame volcanoes for a gas spike on Venus, even though Venus has volcanic mountains and that's how it works on Earth, because we haven't seen a volcano erupting there and the gas might just change on its own.

Conclusion: One should not conclude that volcanic activity was the cause of the sulfur dioxide spike detected on Venus.

Reasoning: No active volcanoes have been identified on Venus yet, and atmospheric chemical levels are known to fluctuate naturally in cycles.

Analysis: The scientist's argument is essentially an 'absence of evidence' play; they claim that because we haven't seen an active volcano, we shouldn't assume one exists. To weaken this, we need to suggest that the 'natural cycles' are actually caused by volcanoes or that our inability to see an active volcano is due to technical limitations rather than their absence. Look for an answer that links the sulfur dioxide cycles directly to volcanic processes or explains why we might miss an eruption.