Immigrants along the Yangtze River in Heilongjiang

Analysis of test questions: This question mainly examines students' ability to solve practical problems by using the historical knowledge they have learned. The population of modern China flocked to the economically developed coastal areas along the Yangtze River because China was gradually involved in the capitalist world market after the Opium War. With the opening of trading ports, the modern industrialization in the southeast coastal areas of China started earlier, the urbanization process began to accelerate, and the export-oriented characteristics of China's economic development became increasingly obvious. Therefore, C and A B D are both correct answers, but all three are the causes of immigration, not the result of immigration tide.