In order to implement the strategy of strengthening the city by culture, in 2008, two libraries have been built in 2008 and 2010. At the end of 2008, a total of more than 70,000 citizens 'library cards were processed, and by the end of 2010, a total of 130,000 citizens' library cards were processed. In the year, the city established a third library in the new district, which was completed and opened in early 2012. As of the end of 2012, the city had handled more than 200,000 citizens' library cards, and the city government believed that this measure was effective. Because in just 4 years, the number of citizens patronizing the library has almost tripled. Which of the following, if true, would most weaken the conclusion? ['The library has to constantly purchase new books, and the maintenance cost is also high, which will affect the construction of other cultural facilities in the city.', 'There are two colleges and universities in the city, and many students have also applied for library debit cards from these three libraries.', 'Many citizens who have applied for the first library card have also applied for two other libraries.', "The city's new district construction is developing rapidly, and a large number of immigrants have poured into the new district in 4 years."]