Passage Summary: A wall is bulging, and since only a broken support beam can cause a bulge, one of the beams must be broken.

Conclusion: At least one of the joists supporting the wall is currently broken.

Reasoning: The wall has a specific defect (a bulge), and the only possible cause for that defect is a broken joist.

Analysis: The structure is: Effect E exists; only Cause C can produce Effect E; therefore, Cause C must exist. This is a valid deductive argument based on a necessary condition for the effect. When looking for a match, ensure the premise establishes an exclusive cause ('the only thing') and the conclusion confirms that cause occurred because the effect is present.