Which of the following most logically completes the passage?

The Roman emperors issued coins made of a silver-copper alloy. Over time the silver content in the alloy used for minting was reduced from an original 90% to less than 10%. The coins, however, continued to appear silver on the outside. It is therefore tempting to suspect that the silver surfaces were added to hide the reduction in silver content. However, that suspicion is probably groundless, since ______.

In areas with limited access to motorized transportation, farmers plant crops as close as possible to their homes to minimize the walking required to reach their fields and the work required to transport their harvest back to their homes. Farmers have almost no motorized transportation in certain parts of Africa where cassava is an important food crop. Although by no means the easiest to transport, cassava is invariably the crop planted farthest from these farmers' villages.

Which of the following, if true, provides the best explanation for the relative placement of the cassava crops?

Lead poisoning in children can cause serious brain damage and impaired development. Because ingestion of lead-based paints is the most common cause of lead poisoning among children, Centerville passed a law five years ago requiring the removal of lead-based paint from the walls of any house or apartment containing children. Yet, in the years since the law was passed, the number of new lead-poisoning cases among Centerville children has substantially increased.

Which of the following, if true would most help to explain why the number of cases of lead poisoning has increased despite the law about paint removal?

Which of the following most logically completes the argument?

It has been observed that in Britain a majority of the people admitted to elite universities have a last name beginning with a letter in the first half of the alphabet. Some have suggested that these data indicate a bias that could originate in the way admissions files are stored or possibly in school classroom seating arrangements； if those are alphabetically based. However, the observation actually provides no evidence for any alphabetic bias in university admissions, since _________.     

In an experiment, one group of volunteers was shown words associated with money, such as "salary, whereas another group was shown neutral words. Afterward, individuals in both groups solved puzzles unrelated to money. Those who had been shown words associated with money were much less likely to request or offer help with the puzzles. The researchers concluded from this evidence that preoccupation with money makes people less cooperative.

Which of the following is an assumption the researchers' reasoning requires?

We know very little about the Etruscans, whose civilization flourished in central Italy from the ninth to the second centuries BC, and much of what we do know comes from their art, for the Etruscan language is all but ciphers to us. Greek and Phoenician sources indicate that the Etruscans enjoyed trade and commerce with those societies, by which the Etruscans were doubtless influenced. Yet unlike women in those societies, women in Etruscan society participated in important social functions, as documented by several Etruscan artworks. Thus, the Etruscan women held unusual status and freedom for the time and region.

The argument above requires which of the following assumptions?

Research shows that over half of all morning political talk shows on the major television networks do not include any women broadcasters, and in terms of total guest appearances on these shows, women represent just 14 percent of the guests. Why does this research matter? These shows are a critical forum for our nation's political debates. They have an agenda-setting effect, in that they tend to influence the priorities of citizens across the country. The relative lack of women on these shows results in women's issues being a lower political priority for most citizens.

The argument above relies on which of the following assumptions?

The government has warned of possible travel disruptions this winter because the primary chemical used to keep airport runways free of snow and ice is scarce. There are effective alternative chemicals. However, they are environmentally hazardous and thus require special exemptions from the ban on their use. So if the government issued such exemptions to cold-weather airports, travelers would not have to face the warned-of travel disruptions.

Which of the following is an assumption on which the argument depends?

Studies have shown that people are swayed more by communications they believe are not intended to persuade than by those they believe are. Many politicians use this to their advantage by giving the impression of impromptu speech, when in fact their rhetoric is carefully scripted. Politicians who are skilled at giving this impression are thus able to convince many otherwise resistant listeners to adopt their point of view.

Which of the following is an assumption required by the explanation above?

Most jurors will be more inclined to reach a verdict favorable to one side if that side's case is based primarily on eyewitness testimony rather than on physical evidence backed by expert scientific testimony. Surprisingly, studies involving jurors in mock trials have found that this tendency survives even for those jurors who understand that eyewitness testimony is generally less reliable than is physical evidence backed by expert testimony.

Which of the following, if true, would most help to explain the surprising phenomenon described above?