According to the World Bank's World Development Report 1990, the proportion of middle school students in the twelve to seventeen-year-old population is 93% in high-income countries, 67% in upper-middle-income countries, 49% in lower-middle-income countries, and 26 in low-income countries. %, The lowest income country is 12%; college students account for the proportion of 20 to 24 years old, 39% in high-income countries, 20% in upper-middle-income countries, 16% in lower-middle-income countries, and 3% in low-income countries, The lowest income country is 2%. What is the main point supported by this passage? ['Comparing the proportion of the average age of middle and college students, high-income countries are higher than low-income countries.', 'The advancement and backwardness of the economy determine the level of national quality.', "National quality determines the development of a country's economy.", "The development of a country's economy is closely related to the situation of national quality."]