Which of the following is NOT a method of improving air quality?

Dispensing with public transportation is not a method of improving air quality because public transportation systems are designed to reduce the number of individual vehicles on the road. When people use public transport, it decreases traffic congestion and lowers greenhouse gas emissions and other pollutants that contribute to air quality deterioration. The other options—promoting fuel efficiency standards, implementing cleaner fuels, and enhancing public transport usage—all contribute positively to air quality by reducing emissions and reliance on fossil fuels. Therefore, eliminating public transportation would likely lead to poorer air quality, making it the correct answer to the question.