Text structure and purpose

A juvenile octopus can solve a maze it has never seen. It can also open a jar, once. Researchers who test the same animal a week later find that it must work the problem out again from the beginning, and that an animal which first opened a jar in ninety seconds will take nearly as long on its second attempt. Octopuses are widely described as intelligent, and by most measures they are. What they appear to lack is a way of carrying a solution forward in time.

Which choice best describes the function of the sentence "Octopuses are widely described as intelligent, and by most measures they are" in the text as a whole?

• A) It concedes a general point before the text identifies a specific exception to it. ✓
• B) It explains why researchers chose to study octopuses rather than other animals.
• C) It introduces a claim that the remainder of the text goes on to refute.
• D) It provides evidence for the maze-solving ability described earlier.

Why: The sentence grants the standard view that octopuses "by most measures" are intelligent, and the passage then narrows that concession by identifying what they "appear to lack": "a way of carrying a solution forward in time." "It explains why researchers chose to study octopuses rather than other animals." claims the sentence explains a research decision about which animals to study, but the passage gives no reason for why octopuses were chosen over other species. "It introduces a claim that the remainder of the text goes on to refute." treats the sentence as introducing a claim the passage will "refute," but the passage never denies octopus intelligence outright; it qualifies it with a specific limitation instead. "It provides evidence for the maze-solving ability described earlier." claims the sentence provides evidence for the maze-solving ability described earlier, but the sentence instead makes a broader concession about intelligence in general, separate from the maze example.

Genes for antibiotic resistance turn up in soil sampled from permafrost thousands of years old, long before any clinic existed. Resistance is therefore not something medicine created but something medicine selected for. Soil bacteria compete by secreting antibiotics, and neighbors that survive them carry the genes that allow it. What hospitals changed was the scale of the advantage. A gene that once helped in scattered patches of soil now helps everywhere a drug is used, which is nearly everywhere. The gene did not change; the value of holding it did.

Which choice best describes the function of the underlined sentence ("Resistance is therefore not something medicine created but") in the text as a whole?

• A) It predicts that resistance genes will continue to spread through soil bacteria wherever antibiotics are used.
• B) It concedes that the permafrost samples described in the first sentence may have been contaminated by modern soil.
• C) It explains the biological mechanism by which soil bacteria come to carry genes for antibiotic resistance.
• D) It states the conclusion that the opening finding licenses and that the rest of the text qualifies and explains. ✓

Why: The permafrost genes license the conclusion that medicine "selected for" rather than created resistance, and the remainder both explains why (soil competition) and qualifies the claim by noting that hospitals changed "the scale of the advantage." Choice C belongs to the following sentence. Choice A makes a prediction the sentence does not contain. Choice B supposes a doubt about contamination that the text never raises. It concedes that the permafrost samples described in the first sentence may have been contaminated by modern soil. is no doubt about the samples is raised anywhere in the text. It predicts that resistance genes will continue to spread through soil bacteria wherever antibiotics are used. is a prediction is implied by the last sentence, not made by this one. It explains the biological mechanism by which soil bacteria come to carry genes for antibiotic resistance. is that mechanism is given in the next sentence, about secretion and survival.

Economists studying tipping have generally treated it as a payment for service quality. Surveys find, however, that the correlation between rated service and tip size is weak, and that tip percentages barely change between a memorable meal and a mediocre one. One review pooling dozens of restaurant studies found that rated service accounted for only a few percent of the variation in what diners left. What does predict tip size is the presence of other diners at the table. Tipping, on this evidence, looks less like a rating than like a performance for an audience.

The passage suggests that the weaknesses in the standard economic interpretation of tipping are primarily revealed through which of the following?

• A) the observation that memorable meals receive only slightly larger tips than mediocre ones
• B) evidence that tips vary significantly depending on whether other diners are present
• C) data demonstrating that diners consciously use tipping as a social performance rather than service evaluation
• D) contradictions between survey findings about service ratings and actual tipping behavior ✓

Why: The passage sets the standard economic view against survey evidence that "the correlation between rated service and tip size is weak," and one review found "rated service accounted for only a few percent of the variation in what diners left," a direct contradiction of what the standard interpretation would predict. The choice "the observation that memorable meals receive only slightly larger tips than mediocre ones" names only a single piece of evidence, not the broader pattern of weak correlation across studies that actually reveals the interpretation's weakness. The choice "evidence that tips vary significantly depending on whether other diners are present" describes what the passage says does predict tip size, a new finding, rather than the contradiction that undermines the old, service-based interpretation. The choice "data demonstrating that diners consciously use tipping as a social performance rather than service evaluation" overstates the passage, which says tipping merely "looks less like a rating than like a performance," an inference by the author, not a claim about diners' conscious awareness. The weakness in the standard interpretation is revealed through the contradiction between what survey findings show about service ratings and what actual tipping behavior looks like.