Over the last few decades, public outcries against pollution have brought about stricter regulations of emissions. The cities that had the most polluted air 30 years ago now have greatly improved air quality. This would not have happened without these stricter regulations. Which one of the following can be properly inferred from the statements above? ['Public criticism led to an improvement in the air quality of the cities that had the most polluted air 30 years ago.', 'Most of the public outcries against pollution came from people in the cities that had the most polluted air.', 'In the city with the worst air pollution today, the air quality is better than it was 30 years ago.', 'The most polluted cities today are not the cities that were the most polluted 30 years ago.']