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 do not 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 of 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 requires 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 grandparents，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.

　　1. Another good title for this passage would be_____.

　　A) What Makes a Family?

　　B) The Life of the Inuits.

　　C) Living with Hardship.

　　D) The Failure of the Nuclear Family.

　　2. A nuclear family is defined as_____.

　　A) a married couple with their minor children

　　B) a single father with，minor children

　　C) parents，grandparents，and children

　　D) parents，children，and aunts and uncles

　　3. The information in this passage would most likely be found in_____.

　　A) an anthropology textbook

　　B) a biology textbook

　　C) a mathematics textbook

　　D) a geography textbook

　　4. The information in the first paragraph is presented mainly through _____.

　　A) listing statistics

　　B) telling a story

　　C) pointing out similarities

　　D) pointing out differences

　　5. The word mobility means_____.

　　A) money

　　B) readiness to move

　　C) organization

　　D) skill