Paragraph 4 answers which of the following questions about China's population growth between 1400 and 1965? A. Which figures relating to China's population growth were unreliable? B. Why did Dwight Perkins assume that China's population in 1400 was about 80 million? C. Where in China did most of the population increase take place? D. What factors made China's population growth between 1400 and 1965 possible?