31. Which of the following statements, if true, can be used to counter the author's argument?(A) The population density in China is 145 people per square kilometer.(B) The median household income in Illinois is 56,210 while that in the countryside area of Illinois is 58,141.(C) Beijing and Pyongyang had signed an agreement to grant 40,000 industrial trainee visas to North Koreans to permit them to work in China.(D) The GDP per capita of a country with a population density higher than 350 people per square kilometer is usually lower than that with a density lower than 350 people.