Passage 3
The structure of a family takes different forms around the world and even in the same society. The family's form changes as it adapts to changing social and economic influences. Until recently, the most common form in North America was the nuclear family, consisting of a married couple with their minor children. The nuclear family is an independent unit. It must be prepared to fend for itself. Individual family members strongly depend on one another. There is little help from outside the family in emergencies. Elderly relatives of a nuclear family are cared for only if it is possible for the family to do so. In North America, the elderly often don't live with the family; they live in retirement communities and nursing homes.
There are many parallels between the nuclear family in industrial societies, such as North America, and families in societies such as that of the Inuits, who live in harsh environments. The nuclear family structure is well adapted to a life of mobility. In harsh conditions, mobility allows the family to hunt for food. For North Americans, the hunt for jobs and improved social status also required mobility.
The nuclear family was not always the North American standard. In a more agrarian time, the small nuclear family was usually part of a larger extended family. This might have included grand-parents, mother and father, brothers and sisters, uncles, aunts and cousins. In North America today, there is a dramatic rise in the number of single-parent households. Twice as many households in the United States are headed by divorced, separated or never-married individuals as are comprised of nuclear families. The structure of the family, not just in North America, but throughout the world, continues to change as it adapts to changing conditions.
The best title for this passage would be ________.
全文主旨题。全文主旨句为第一段第一句The structure of a family takes different forms around the world and even in the same society（全世界即使是同一个社会家庭结构也有所不同）。接下来两段都是在讲述南美洲及南美洲以外的家庭结构，所以本题答案选A。
A nuclear family is defined as a family that includes ________.
第一段第二句话给南美洲的核心家庭进行了定义即consisting of a married couple with their minor children（一对已婚夫妇和未成年子女组成的家庭）。所以选C。
Which of the following is not given as a reason for mobility?
第二段是关于mobility的原因。第二段结尾接连提到了流动性的 原因In harsh conditions, mobility allows the family to hunt for food. For North Americans, the hunt for jobs and improved social status also required mobility。提取关键词为harsh conditions（环境恶劣）、hunt for food（找食物）、hunt for jobs（找工作）以及improved social status（提升社会地位）。由此可知，A、B、C都为流动的原因，所以本题选D。
Which new trend is observed in the family structure in North America today?
由最后一段第三句话In North America today, there is a dramatic rise in the number of single-parent households（如今，在南美洲，单亲 家庭的数量急剧攀升）。所以在南美洲的家庭趋势为单亲家庭，答案选A。
The information in this passage would most likely be found in ________.
推断题。综合全文是在讲人类家庭的演变发展，所以这篇文应该会出现在人类学书籍中，答案选D。