A recent survey shows that in recent years, locals have accounted for more than 70% of high-income people in a city, which fully shows that it is quite difficult for foreigners to obtain high income in the city. Which of the following is true if it supports the above conclusion? ["Foreigners make up 40% of the city's total population.", "Foreigners make up less than 30% of the city's total population.", 'Foreigners make up 40% of the city ’s low- and middle-income population.', "Locals make up less than 30% of the city's low- and middle-income population."]