The topic mainly examines the ability to analyze and compare similar content. This topic examines the relevant positions of the great powers that forced the Qing Dynasty to open ports and trade in modern history, and deepens the correct understanding of the invasion of China by the great powers. A is in the middle reaches of the Yangtze River, B and D are in the lower reaches of the Yangtze River, and C is in the upper reaches of the Yangtze River, which is the deepest inland. Correct answer.