Chapter 2

Nuclear fusion is a process whereby the nuclei of atoms are jouned, or "tused," and in which energy is released. One of the by-products of fusion is helium \(-4\) gas. A recent fusion experiment was conducted using "heavy" water contained in a sealed flask. The flask was, in turn, contained in an air- filled chamber designed to eliminate extraneous vibration. After the experiment, a measurable amount of helium-4 gas was found in the air of the chamber. The experimenters cited this evidence in support of their conclusion that fusion had been achieved. Which one of the following, if true, would cast doubt on the experimenters' conclusion? (A) Helium-4 was not the only gas found in the experiment chamber. (B) When fusion is achieved, it normally produces several by-products, including tritium and gamma rays. (C) The amount of helium-4 found in the chamber's air did not exceed the amount of helium-4 that is found in ordinary air. (D) Helium-4 gas rapidly breaks down, forming ordinary helium gas after a few hours. (E) Nuclear fusion reactions are characterized by the release of large amounts of heat.

Every photograph, because it involves the light rays that something emits hitting film, must in some obvious sense be true. But because it could always have been made to show things differently than it does, it cannot express the whole truth and, in that sense, is false. Therefore, nothing can ever be definitively proved with a photograph. Which one of the following is an assumption that would permit the conclusion above to be properly drawn? (A) Whatever is false in the sense that it cannot express the whole truth cannot furnish definitive proof. (B) The whole truth cannot be known. (C) It is not possible to determine the truthfulness of a photograph in any sense. (D) It is possible to use a photograph as corroborative evidence if there is additional evidence establishing the truth about the scene photographed. (E) If something is being photographed, then it is possible to prove definitively the truth about it.

Leaming how to build a nest plays an important part in the breeding success of birds. For example, Dr. Snow has recorded the success of a number of blackbirds in several successive years. He finds that birds nesting for the first time are less successful in breeding than are older birds, and also less successful than they themselves are a year later. This cannot be a mere matter of size and strength, since blackbirds, like the great majority of birds, are fully grown when they leave the nest. It is difficult to avoid the conclusion that they benefit by their nesting experience. Which one of the following, if true, would most weaken the argument? (A) Blackbirds build better nests than other birds. (B) The capacity of blackbirds to lay viable eggs increases with each successive trial during the first few years of reproduction. (C) The breeding success of birds nesting for the second time is greater than that of birds nesting for the first time. (D) Smaller and weaker blackbirds breed just as suecessfully as bigger and stronger blackbirds. (E) Up to 25 percent of all birds are killed by predators before they start to nest.

Assume that a person who lives in a small, wellinsulated house that contains toxin-releasing products places houseplants, such as those tested, in the house. Which one of the following can be expected as a result? (A) There will no longer be any need to ventilate the house. (B) The concentration of toxins in the household air supply will remain the same. (C) The house will be warm and have a safe air supply. (D) If there is formaldehyde in the household air supply, its level will decrease. (E) If formaldehyde and benzene are being released into the household air supply, the quantities released of each will decrease.

How do the airlines expect to prevent commercial plane crashes? Studies have shown that pilot error contributes to two-thirds of all such crashes. To address this problem, the airlines have upgraded their training programs by increasing the hours of classroom instruction and emphasizing communication skills in the cockpit. But it is unrealistic to expect such measures to compensate for pilots lack of actual flying time. Therefore, the airlines should rethink their training approach to reducing commercial crashes. Which one of the following is an assumption upon which the argument depends? (A) Training programs can eliminate pilot errors. (B) Commercial pilots routinely undergo additional training throughout their careers. (C) The number of airline crashes will decrease if pilot training programs focus on increasing actual flying time. (D) Lack of actual flying time is an important contributor to pilot error in commercial plane crashes. (E) Communication skills are not important to pilot training programs.

All savings accounts are interest-bearing accounts. The interest from some interest-bearing accounts is tax-free, so there must be some savings accounts that have taxfree interest. Which one of the following arguments is flawed in a way most similar to the way in which the passage is flawed? (A) All artists are intellectuals. Some great photographers are artists. Therefore, some great photographers must be intellectuals. (B) All great photographers are artists. All artists are intellectuals. Therefore, some great photographers must be intellectuals. (C) All great photographers are artists. Some artists are intellectuals. Therefore, some great photographers are intellectuals. (D) All great photographers are artists. Some great photographers are intellectuals. Therefore, some artists must be intellectuals. (E) All great photographers are artists. No artists are intellectuals. Therefore, some great photographers must not be intellectuals.

Normal full-term babies are all born with certain instinctive reflexes that disappear by the age of two months. Because this three-month-old baby exhibits these reflexes, this baby is not a normal full-term baby. Which one of the following has a logical structure most like that of the argument above? (A) Because carbon dioxide tums limewater milky and this gas is oxygen, it will not turn limewater milky. (B) Because no ape can talk and Suzy is an ape, Suzy cannot talk. (C) Because humans are social animals and Henry is sociable, Henry is normal. (D) Because opossums have abdominal pouches and this animal lacks any such pouch, this animal is not an opossum. (E) Because some types of trees shed their leaves annually and this tree has not shed its leaves, it is not normal.

One method of dating the emergence of species is to compare the genetic material of related species. Scientists theorize that the more genetically similar two species are to each other, the more recently they diverged from a common ancestor. After comparing genetic material from giant pandas, red pandas, raccoons, coatis, and all seven bear species, scientists concluded that bears and raccoons diverged 30 to 50 million years ago. They further concluded that red pandas separated from the ancestor of today's raccoons and coatis a few million years later, some 10 million years before giant pandas diverged from the other bears. Which one of the following can be properly inferred from the passage? (A) Giant pandas and red pandas are more closely related than scientists originally thought they were. (B) Scientists now count the giant panda as the eighth species of bear. (C) It is possible to determine, within a margin of just a few years, the timing of divergence of various species. (D) Scientists have found that giant pandas are more similar genetically to bears than to raccoons. (E) There is substantial consensus among scientists that giant pandas and red pandas are equally related to raccoons.

Efficiency and redundancy are contradictory characteristics of linguistic systems; however, they can be used together to achieve usefulness and reliability in communication. If a spoken language is completely efficient, then every possible permutation of its basic language sounds can be an understandable word. However, if the human auditory system is an imperfect receptor of sounds, then it is not true that every possible permutation of a spoken language's basic tanguage sounds can be an understandable word. If all of the statements above are true, which one of the following must also be true? (A) Efficiency causes a spoken language to be useful and redundancy causes it to be reliable. (B) Neither efficiency nor redundancy can be completely achieved in spoken language. (C) If a spoken language were completely redundant, then it could not be useful. (D) If the human auditory system were a perfect receptor of sounds, then every permutation of language sounds would be an understandable word. (E) If the human auditory system is an imperfect receptor of sounds, then a spoken language cannot be completely efficient.

All intelligent people are nearsighted. I am very nearsighted. So I must be a genius. Which one of the following exhibits both of the logical flaws exhibited in the argument above? (A) I must be stupid because all intelligent people are nearsighted and I have perfect eyesight. (B) All chickens have beaks. This bird has a beak. So this bird must be a chicken. (C) All pigs have four legs, but this spider has eight legs. So this spider must be twice as big as any pig. (D) John is extremely happy, so he must be extremely tall because all tall people are happy. (E) All geniuses are very nearsighted. I must be very nearsighted since I am a genius.