答案：

　　Part Ⅳ Reading Comprehension (Reading in Depth)

　　Section A

　　47. divorced from reality/unrealistic

　　48. The backbreaking labor of the working poor. /The bowed backs of the working poor.

　　49. (their) lack of skill/(their)low skill

　　50. much greater

　　51. Poor.

　　试题解析：

　　Part Ⅳ Reading Comprehension(Reading in Depth)

　　Section A

　　47.文章一开始作者讲到美国人一直相信这样一个神话：只要工作就有回报，工作的人完全可以养家.但紧接着作者说“It's a myth that has become so divorced from reality that it might as well begin with the words‘Once upon a time.”(这个神话和现实有如此大的差距以至于我们在这么说之前得加上“很久很久以前……”。)所以本题可以填写原文中的原词“divorced from reality”.这样要填写的句子的意思就符合原文了，作者说“我们最好在前面加上很久很久以前”，暗示美国神话已经脱离了现实。基于对这部分意思的理解，也可以填写“unrealistic”，表示这一神话般的说法是不现实的。

　　48.第一段最后一句“The American Dream for the well-to-do grows from the bowed backs of the working poor，who too often have to choose between groceries and rent.”中的grows from和问题中的is built upon是一个意思。因此，本题可以用“The bowed backs of the working poor，”来回答，也可以基于理解，回答成“The backbreaking labor of the working labor”。

　　49.第三段第一句“We ease our consciences，Shulman writes，by describing these people as ‘low skilled，’ as though they're not important or intelligent enough to deserve more.”中的“ease our consciences”就是“减轻负疚感”的意思。因此只要回答归咎于劳动者“技能低下”就可以了。原文用的是形容词“low skilled”，题目中在介词to后用名词。因此答案可以是“(their)lack of skill”或者“(their) low skill”。

　　50.第三段倒数第二句，“While the bottom 10 percent of American workers earn just 37 percent of our average wage，their，counterparts in other industrialized countries earn upwards of 60 percent.”中提到美国工资最低的10%的劳动者的收入占美国人均收入的37%，而在其他工业国家，这类劳动者的收入达到这些国家平均收入的60%。由此可见，美国劳动者的最低收入和人均收入的差距要比其他工业国家的大很多。因此，正确答案为“much greater”。

　　51.文章最后一段说“Almost 40 years ago，when Lyndon Johnson declared war on poverty，a family with a car and a house in the suburbs felt prosperous.Today that same family may well feel poor...”。可见正确答案是“Poor”。