Passage Summary: Since the flu shot worked perfectly for everyone who took it last year, and every student took it this year, the author concludes the school will be flu-free.

Conclusion: No students at South High School will contract the flu this season.

Reasoning: In a previous year, everyone who was vaccinated avoided the flu, and this year every student at the school has been vaccinated.

Analysis: The reasoning structure here is: 'In the past, condition X led to result Y; condition X is present now, so result Y will occur again.' It assumes that a past success rate is a perfect predictor for a current group. When looking for a parallel, find an argument that takes a past correlation or cause-effect relationship and applies it as a guarantee for a new, specific population. The logic is a bit optimistic, as it ignores the possibility that circumstances (or flu strains) might change.