试题题干
In the first half of the twentieth century, black Americans were attracted from southern farms to northern cities in（ ）.
参考答案
正确答案：
试题解析
本题考查美国的人口迁移。
Similarly, economic opportunities in industrial, northern cities attracted black Americans from southern farms in the first half of the 20th century, in what was known as the Great Migration.
同样，20世纪上半叶，北方工业城市的经济机会吸引了来自南方农场的美国黑人，这就是所谓的大迁徙。故选B。