单选题 The living standards of the new immigrants were improved in the late nineteenth and early twentieth centuries mainly because

A、 they kept the political bosses in power.
B、 the political bosses gave them a lot of practical help.
C、 they had a much stronger feeling of being a part of the larger culture.
D、 there was a rapid growth in American economy at that time.

【正确答案】 D

【答案解析】[解析] 本题考查事实细节。十九世纪末、二十世纪初，移民生活水平提高的主要原因是什么?答案在最后一段第三句：世纪之交时，美国经济的迅速发展，再加上有政治老板的帮助，移民的生活水平提高了。所以，美国经济的迅速发展是移民生活水平提高的主要原因，而政治老板的帮助是次要原因。题目问的是主要原因，[B]是次要原因，应被排除。