Passage Summary: A city destroyed 60 of its 100 big buildings. Since big buildings indicate a healthy economy, the author says the city's economy is failing.

Conclusion: Downtown Petropolis is currently experiencing a major economic decline.

Reasoning: The number of large buildings is a sign of economic health, and 60 of the 100 large buildings that existed five years ago have been demolished.

Analysis: The author is focusing entirely on the '60 demolished' figure while ignoring the possibility of new construction. If the city demolished 60 old buildings but built 80 new ones, the total number of large buildings would actually increase, suggesting economic growth rather than decline. For the argument to work, it must assume that the total number of large buildings has actually gone down. Look for an answer that addresses the lack of replacement buildings.