Most water companies in the United States add fluoride to tap water to help prevent cavities. Some dentists argue, however, that this practice actually causes more harm than good because people overestimate the protection afforded by the fluoride and do not take the proper steps to care for their teeth, such as brushing and flossing after every meal. If water companies did not add fluoride, the dentists claim, people would be forced to be more active in their dental hygiene and tooth decay would decline as a result.

Which of the following, if true, most weakens the dentists' claims?

Footwear designer John de los Santos last year released several limited editions of his best-known model of sneaker in exotic colors and prints. Although the new releases were priced substantially higher than their counterparts in more traditional colors, they sold out within a week of their release, and have since been selling on the resale market for up to four times the original price. The cost of producing the sneakers in exotic prints is no greater than that of producing them in more traditional colors, so de los Santos could earn a higher profit per unit by producing a greater percentage of his sneakers in such prints.

Which of the following is an assumption made in drawing the conclusion above?

Weight loss programs that guarantee results mislead their customers. No program can ensure that someone who follows it will lose weight. These programs prey upon unhappy and insecure people who are often driven more by emotion than by reason. Moreover, many people who lose weight while on a program eventually regain the weight within a year. So while the programs' claims may be true for a short period, customers will be disappointed in the long run.

The two portions in boldface play which of the following roles?

Country X contains many rivers that flow down from its high mountains. These rivers have been dammed to harness the hydroelectric power that can be derived from this resource. Enough power is generated to create a reserve that is more than enough to meet the country's year-round energy needs. Yet, citizens of Country X often experience power shortages or even outages.

Which of the following, if true, best explains the situation described above?

Researchers have noticed that people whose blood shows abnormally low levels of calcium usually have laryngeal polyps, which can permanently damage vocal cords and result in partial or even total loss of voice. In order to reduce the risk of polyps, the researchers recommend a diet high in calcium-rich foods such as dairy and green, leafy vegetables.

Which of the following, if true, most strongly suggests that following the researchers' recommendation would NOT be effective?

Company X conducted a taste test to determine whether its new soft drink had a good chance of commercial success. A sample of consumers was asked to compare the flavor of the new soft drink to that of an established brand without knowing the true identity of either beverage. Overwhelmingly, the consumers preferred the taste of the proposed soft drink to that of the established brand. Clearly, Company X has a good chance of commercial success with its new soft drink.

Which of the following, if true, would most seriously weaken the argument above?

According to a study concerning environmental economics, any manufacturer that offers an environmentally sound lawnmower, such as a manual push mower, will almost certainly reap a huge profit because consumers say that they want a mower that requires neither gasoline nor electricity. A spokesman for the trade association of gasoline lawnmower manufacturers asserted that this claim had little factual support.

Which of the following, if true, would best support the claim made by the spokesperson?

Any government action that intrudes on the right of privacy of an individual is unconstitutional. Therefore, the requirement that students in public school submit to random locker searches is unconstitutional.

Which of the following, if true, most weakens the conclusion that random locker searches in public schools are unconstitutional?

Consumer advocate: Ephedra is a naturally occurring compound that some people use as a weight-loss aid. Recently, the government prohibited the sale of dietary supplements containing ephedra on the grounds that ephedra has been shown to have grave side effects. This prohibition is unreasonable. Echinacea is another natural compound that has been shown to have side effects, yet echinacea is widely available at health food stores.

The consumer advocate's argument depends on which of the following assumptions?

More and more companies have begun to consume less energy by making themselves more efficient. Over time, these efforts could place the United States at the forefront of an emerging global market for cleaner technologies. Such efforts are also essential to tackling the two big energy-related issues of the age: global warming and the dependence on precarious supplies of oil. The federal government should encourage these efforts by providing the necessary incentives, whether as loans, direct grants or targeted tax breaks.

Which of the following, if true, provides the most effective support for the argument?

More than 80% of the executives in the county attended high school in the county, and clearly they represent some of the brightest in the county. Among the seventeen high schools in the county, the three in the coastal towns have had the highest test scores in the county for several decades. A recent study shows that almost all of the county executives who attended high school in the county attended one of those three high schools in the coastal towns. The argument above is most vulnerable to criticism on which grounds?

Two years ago, the human resources department at Harrison's Technologies had 175 sexual harassment cases open, a number that at that time led all companies in the sector. At that time, a typical claim took six months to process and clear. In response to this high number, the CEO's Advisory Team published a comprehensive set of guidelines for training employees in the identification and avoidance of behaviors that could constitute sexual harassment. At this writing, the human resources department has only sixty sexual harassment cases open. Clearly, the guidelines published by the CEO's Advisory Team were effective in reducing the occurrence of new sexual harassment claims at Harrison's Technologies. Which of the following, if true, most seriously weakens the conclusion above?

The Dvorak keyboard requires less finger movement than the ubiquitous QWERTY keyboard. As a result, Dvorak keyboard users are not only able to type more words per minute, but are also less vulnerable to both repetitive stress disorder and carpal tunnel syndrome. Nonetheless, businesses, as well as consumers, have not adopted the Dvorak keyboard. Clearly, if the Dvorak keyboard is to become more widely used, its benefits must be more widely touted. Which of the following, if true, casts the most doubt on the author's conclusion?

Traditionally, the most highly sought cars have been the "sports cars" and similar two-door models. Nevertheless, Zincstone Motors has chosen to eliminate the last two-door models and produce only four-door models.Which of the following would, if true, most help to explain Zincstone Motors' strategy?

Dolphins can swim at high speeds and achieve high acceleration in the water. In 1936, Sir James Gray calculated the force dolphins should be able to exert based on their physiology. He concluded that the propulsive force they were able to exert was not enough to explain how fast they swim and accelerate. In the 2000s, experimenters used special computer-enhanced measurements of the water in which dolphins were swimming. Through mathematical modeling, they were able to measure the force dolphins exert with their tails. As it turns out, dolphins exert considerably more force with their tails than Sir James Gray or anybody else ever expected. Therefore, the force exerted by their tails easily explains how fast they swim and accelerate.In the argument, the two portions in boldface play which of the following roles?