A map of Modern China. A key shows People per kilometer squared by color. Pink is 200 plus, purple is 100 to 200, green is 10 to 100, orange is 0 to 10. The Yellow River, Yangtze River, and Xi River are in the northeast of China. The Plateau of Tibet in Western China is orange. The North China Plain and regions surrounding the rivers are pink, purple, and green. Study the two maps. Then, use the drop-down menus to answer the questions.

What part of ancient and modern China has a high population density?

How has the population of the Yangtze River valley changed over time?

What area is least populated, both in the present and in the past?