Passage Summary: An astronomer claims their theory is true simply because no one has been able to prove it's false yet.

Conclusion: The astronomer's theory regarding the cause of lunar cratering is correct.

Reasoning: Opponents have failed to prove the theory false, and their evidence against it is inconclusive.

Analysis: This is a textbook "Appeal to Ignorance" fallacy. The astronomer is confusing a "lack of evidence against a claim" with "positive evidence for a claim." Just because your opponents can't prove you're wrong doesn't mean you've been proven right; it might just mean everyone is still guessing. Look for an answer that points out this failure to provide actual supporting evidence for the thesis.