Human migrations （迁移) within recorded history have transformed the entire character of l

Human migrations (迁移) within recorded history have transformed the entire character of lands and continents and the composition of their racial, ethnic and language groups. The map of Europe, for example, is the product of several major early migrations involving the Germanic peoples, the Slaves, and the Turks. The overseas migration of Europeans during this period totaled about 60 million people.

The largest migration in history has been called the Great Atlantic Migration from Europe to North America, the first major wave of which began in the 1840's with mass movements from Ireland and Germany. In the 1880's, a second and larger wave developed from eastern and southern Europe; between 1880 and 1910 some 17 million Europeans entered the United States. The total number of Europeans reaching tile United States amounted to 37 million between 1820 and 1980. From 1801 to 1914 about 7.5 million people moved from Europe to Asiatic Russia, and between World War I and II about 6 million more chose to move there, not counting the vast number of deportees (被遗返回国者) who were forced to go to Siberia's labor camps. Since World War Ⅱ the largest migrations have involved groups from developing countries moving to the industrialized nations. Some 13 million people moved across borders to become permanent residents of Western Europe from the 1960's through the 1980's, and more than 10 million permanent immigrants were admitted Legally to the United States in that same period, with illegal immigration adding several millions more.

Slave migrations and mass expulsions (排斥) also have been part of human history for thousands of years. The largest slave migrations were probably those compelled by European slave traders operating in Africa from the 16th to the 19th century; perhaps 20 million slaves were taken to the America, though a large number died in terrible conditions of the trip across the Atlantic Ocean. The largest mass expulsions have probably been those imposed by Nazi Germany, which deported 7 to 8 million persons during World War Ⅱ. The major trend in internal migration during the 20th century has been the movement from rural to urban areas. As a consequence, urban growth since World War II has been very rapid in much of the world, particularly in developing countries.

What is the main idea of the passage？

A．The map of Europe is the product of several major early migrations.

B．Human migrations within recorded history have changed the world.

C．The overseas migration of Europeans totaled about 60 million people.

D．The first major wave of migration began in the 1840's.