航海家（）的探险活动导致了美洲原住民印第安人文明的毁灭。A、迪亚士 B、哥伦布 C、

设函数f（x）=x|x|+bx+c，给出下列四个命题：

①c=0时，f（x）是奇函数；

②b=0，c＞0时，方程f（x）=0只有一个实根；

③f（x）的图象关于（0，c）对称；

④方程f（x）=0至多两个实根．

其中正确的命题是（　　）

A．①④

B．①③

C．①②③

D．①②④

正方体的棱长扩大到原来的2倍，体积就扩大到原来的8倍。[ ]

在信息系统的物理模型中，表示系统各个物理组成部分之间的数据流动情况的工具是( )。

A．数据流程图

B．业务流程图

C．数据结构图

D．系统流程图

The questions in this group are based on the content of a passage. After reading the passage, choose the best answer to each question. Answer all questions following the passage on the basis of what is stated or implied in the passage.

Of all aspects of Indian culture, the caste system is perhaps the most bewildering to outsiders. For visitors unaccustomed to this system of hereditary social divisions, the complex and mostly unwritten rules governing whom a person can marry, what kind of work she can do, and even what kind of food she can eat may seem puzzling and mysterious. One reason for this confusion is that the concept of caste is actually divided into two separate but related concepts in Indian culture: varna and jati.

Varna, which literally means "color," is the most basic social division. There are four varna: the Brahmans, the traditional priest class; the Kshatriya, the warrior class; the Vaishya, the skilled workers and merchants; and the Sudra, laborers whose role is to serve the three higher classes. Below the Sudra are a class known as the Untouchables, who technically fall outside of the varna system because they are supposedly "unclean" in a ritual sense. The Untouchables are the lowest class in India, but they make life possible for everyone else because they take care of the jobs that would "pollute" the higher classes, such as working with dead animals or cleaning sewage. The Indian statesman Mohandas Gandhi, in an effort to promote social equality, encouraged people to refer to Untouchables as the Harijan, which means "Children of God."

Each varna is then divided into hundreds or thousands of jati, a term that literally means "birth." The jati are kinship groups with hereditary roles and professions, such as leatherworker or brick-maker. Observant Hindus have traditionally married within their varna and jati.

The origins of the caste system are obscure. The prevailing theory among anthropologists is that the Varna system emerged shortly after the so-called Aryan Invasion of the second millennium B.C. According to this theory, a population of Indo-European invaders conquered northern India around 1500 B.C. The Indo-Europeans placed themselves in the three highest rungs of society (Brahman, Kshatriya, and Vaishya), corresponding to the traditional division of Indo-European societies into priests, warriors, and commoners, while placing the conquered local populations into the worker classes of the Sudra and the Untouchables. This theory does not account for the jati system, however, which has parallels in no other Indo-European society. Most anthropologists suggest that the jati system predates the varna system, and that it might have originated in the Harappan civilization that prevailed in northern India prior to the Aryan Invasion.

The final paragraph plays what role in relation to the rest of the passage ？（）

A. It offers information that raises doubts about the conclusions expressed in the previous paragraph.

B. It discusses an alternative view to points stated as facts in the second paragraph.

C. It restates the question raised in the opening paragraph, using information offered in the second and third paragraphs.

D. It offers background information for the system described in the two preceding paragraphs.

E. It summarizes points raised elsewhere in the passage.

二手资料是指在该课题的调研之前已经存在的、自己或他人为其他目的收集到的相关或不相关的资料。