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The correlation between carbon dioxide and temperature throughout the Vostok record is consistent and predictable. The absolute temperature changes, however, are from 5 to 14 times greater than would be expected on the basis of carbon dioxide’s own ability to absorb infrared radiation, or radiant heat. This reaction suggests that, quite aside from changes in heat-trapping gases, commonly known as greenhouse gases, certain positive feedbacks are also amplifying the temperature change. Such feedbacks might involve ice on land and sea, clouds, or water vapor, which also absorb radiant heat. The author mentions "certain positive feedbacks" in order to indicate that

A. increased concentration of carbon dioxide in the Earth’s atmosphere is responsible for global temperature increase.
B. some climate simulation models have produced useful information.
C. greenhouse gases alone do not account for global temperature increase.
D. variables that benefit life are causing global temperature to increase.
E. beneficial substances that are not heat-trapping gases and that contribute to global temperature increase have been found in the Vostok ice core.

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Paule Marshall’s Brown Girl, Brownstones (1959) was a landmark in the depiction of female characters in Black American literature. Marshall avoided the oppressed and tragic heroine in conflict with White society that had been typical of the protest novels of the early twentieth century. Like her immediate predecessors, Zora Neale Hurston and Gwendolyn Brooks, she focused her novel on an ordinary Black woman’s search for identity within the context of a Black community. But Marshall extended the analysis of Black female characters begun by Hurston and Brooks by depicting her heroine’s development in terms of the relationship between her Barbadian American parents, and by exploring how male and female roles were defined by their immigrant culture, which in turn was influenced by the materialism of White America. By placing characters within a wider cultural context, Marshall attacked racial and sexual stereotypes and paved the way for explorations of race, class, and gender in the novels of the 1970’s. The author’s description of the way in which Marshall depicts her heroine’s development is most probably intended to:

A. continue the discussion of similarities in the works of Brooks, Hurston, and Marshall.
B. describe the specific racial and sexual stereotypes that Marshall attacked.
C. contrast the characters in Marshall’s novels with those in later works.
D. show how Marshall extends the portrayal of character initiated by her predecessors.
E. compare themes in Marshall’s early work with themes in her later novels.

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Some recent historians have argued that life in the British colonies in America from approximately 1763 to 1789 was marked by internal conflicts among colonists. Inheritors of some of the viewpoints of early twentieth-century Progressive historians such as Beard and Becker, these recent historians have put forward arguments that deserve evaluation. The kind of conflict most emphasized by these historians is class conflict. Yet with the Revolutionary War dominating these years, how does one distinguish class conflict within that larger conflict Certainly not by the side a person supported. The author most likely refers to historians such as Beard and Becker in order to:

A. isolate the two historians whose work is most representative of the viewpoints of Progressive historians.
B. emphasize the need to find connections between recent historical writing and the work of earlier historians.
C. make a case for the importance of the views of the Progressive historians concerning eighteenth-century American life.
D. suggest that Progressive historians were the first to discover the particular internal conflicts in eighteenth-century American life mentioned in the passage.
E. point out historians whose views of history anticipated some of the views of the recent historians mentioned in the passage.