Passage Summary: You have to be a member to use the gym's pool. Sarah is a member, so the argument claims she definitely uses the pool.

Conclusion: Sarah must use the pool at City Gym at least once in a while.

Reasoning: You need a membership to use the pool, and Sarah has a membership.

Analysis: This argument commits a classic formal logic error by confusing a necessary condition with a sufficient one. The premise establishes that membership is a requirement (necessary) for pool use, but it doesn't say that membership is all you need to guarantee (sufficient) pool use. Sarah might pay for the membership just to use the treadmill or the sauna, or perhaps she just likes supporting the gym. Look for an answer choice that identifies this 'false necessity'—just because she has the permission to use the pool doesn't mean she actually exercises that right.