After the second world war, Europe changed from an emigration area to an emigration area, mainly because of a. After a long period of emigration, the population of Europe

Analysis of test questions: Population migration before World War II was mainly related to geographical discoveries. Population flows from the "old continent" to the "new continent" and from developed areas to underdeveloped areas; After World War II, the economies of western European countries developed rapidly. Due to the difference of social and economic development level, the population flows from relatively backward developing countries to Europe.

Comments: This question is moderately difficult. Great changes have taken place in world population migration before and after World War II, and Europe has changed from emigration to immigration. North America has always been an immigrant area. After World War II, the international population migration is characterized by a significant decline in the proportion of permanent immigrants and a more diversified form of migration.