"A General History of the World" said: "Railways and steamboats effectively transported a large number of people to the oceans and continents ... 65438+only 145000 in the mid-1920s.

Analysis of test questions: According to the narration in the materials, "Railways and steamboats effectively transported a large number of people across the oceans and continents ... In the mid-1920s, only 65,438,045,000 people left Europe", we can see that the inventions in the industrial revolution provided the necessary conditions for immigrants. It took about 20 years from the mid-1950s.

Comments: This topic is causal multiple-choice questions. Usually, the different factors existing in historical phenomena are listed first, and then the corresponding reasons, purposes or results are listed according to the direction of the topic. There are two angles of investigation: the first form infers the reason from the result, and its structure is: the stem is the result, and the alternative is the reason; The second form is to deduce the result or influence from the cause, and its structure is that the problem is the cause and the alternative is the result. Common root causes, direct causes, main causes, etc. First of all, we should correctly understand the meanings of commonly used concepts and their differences and connections, grasp and understand these concepts from the aspects of nature, function and direction, grasp the logical relationship between stem and alternative, make clear who is the cause and who is the result between stem and alternative, contact textbook knowledge, and pay attention to the differences between root, direct cause, subjective reason, objective reason and internal and external cause. Secondly, we should adopt different methods according to the situation.