Passage: For decades, paleontologists interpreted the elaborate cranial crests of hadrosaur dinosaurs as adaptations for underwater feeding, reasoning that the hollow structures could store air. More recent analysis of the crests' internal passages, however, suggests they served instead as resonating chambers for vocalization. The two hypotheses are not strictly exclusive, but the acoustic model better accounts for the striking variation in crest shape among closely related species — variation that would be hard to explain if the crests served a purely respiratory function.
Question: The primary purpose of the passage is to
(A) argue that hadrosaur crests could not have stored air (B) present a newer explanation for a structure and give a reason to prefer it (C) describe the internal anatomy of hadrosaur crests in detail (D) reconcile two competing hypotheses about hadrosaur behavior (E) trace the historical development of paleontological methods
Analysis: The passage lays out an old view (air storage), introduces a newer one (vocalization) at the pivot "however," and then gives a reason to prefer it (species variation). That is exactly choice (B).
Answer: (B).
Passage: Economic historians once attributed the rapid industrialization of the northern United States chiefly to abundant natural resources. Yet the American South possessed comparable resources and industrialized far more slowly. What distinguished the North, some scholars now argue, was institutional rather than material: a dense network of banks, patent offices, and technical schools that allowed inventions to be financed, protected, and diffused.
Question: It can be inferred that the scholars mentioned would most likely agree that
(A) natural resources played no role in Northern industrialization (B) the availability of resources alone is insufficient to explain differing rates of industrialization (C) the American South lacked the resources needed for industry (D) institutional factors are the sole cause of all economic growth (E) the North's technical schools mattered more than its banks
Analysis: North and South had "comparable resources" but industrialized at different rates, so resources alone cannot explain the difference — choice (B), a small step the text forces.
Answer: (B).
Passage: The claim that bilingual children suffer delayed language development has proved remarkably durable despite scant supporting evidence. Early studies that appeared to show such delays typically failed to control for socioeconomic status — a variable now known to affect vocabulary acquisition far more powerfully than bilingualism does. When researchers account for it, the supposed bilingual disadvantage largely disappears.
Question: The author mentions socioeconomic status primarily in order to
(A) identify a factor that undermines the evidence for a bilingual disadvantage (B) argue that bilingualism improves children's language development (C) propose a new method for measuring vocabulary acquisition (D) concede that the early studies were soundly designed (E) explain why bilingual children have smaller vocabularies
Analysis: Socioeconomic status is introduced as the confound the early studies ignored; once it is controlled for, "the supposed bilingual disadvantage largely disappears." Its function is to undermine the evidence for the delay claim — choice (A).
Answer: (A).
Passage: A city installed brighter streetlights in several high-crime neighborhoods and observed that reported crime there fell 15% over the following year. Officials concluded that improved lighting deters criminal activity and announced plans to expand the program citywide.
Question: Which of the following, if true, most weakens the officials' conclusion?
(A) The brighter streetlights consumed significantly more electricity than the old ones. (B) During the same year, the city assigned additional police patrols to those same neighborhoods. (C) Residents of the neighborhoods reported feeling safer after the lights were installed. (D) Crime rates in neighboring cities held steady over the same period. (E) Installing the new lights cost more than officials had anticipated.
Analysis: The conclusion — lighting deters crime — assumes the lighting caused the drop. The gap: some other change might explain it. Choice (B) supplies exactly that alternative cause (extra patrols), directly weakening the causal claim.
Answer: (B).