Summary
Agricultural runoff from a river has caused phosphorus levels to double in an ocean region.
The phosphorus causes the stimulation of plankton growth near the ocean surface.
The plankton decay and fall to the floor, where bacteria eat them and consume oxygen.
This oxygen depletion means that few fish can survive in the region.
The phosphorus causes the stimulation of plankton growth near the ocean surface.
The plankton decay and fall to the floor, where bacteria eat them and consume oxygen.
This oxygen depletion means that few fish can survive in the region.
Very Strongly Supported Conclusions
The agricultural runoff and the phosphorus contribute to the plankton growth, the oxygen depletion, and the fishes’ inability to survive in the region.
A
The agricultural runoff pouring out of the river contributes to the growth of plankton near the ocean surface.
Very strongly supported. The agricultural runoff contributes to the growth of plankton because it caused phosphorus levels to double, which in turn caused the stimulation of plankton growth.
B
Before phosphorus levels doubled in the ocean region, most fish were able to survive in that region.
Unsupported. Higher phosphorus levels have contributed to fish being unable to survive in the region. But we don’t know whether most fish could survive before phosphorus levels doubled.
C
If agricultural runoff ceased pouring out of the river, there would be no bacteria on the ocean floor devouring decaying plankton.
Unsupported. If the agricultural runoff stopped, there might be fewer plankton and fewer bacteria devouring decaying plankton. But we don’t know that there would be no bacteria devouring decaying plankton.
D
The quantity of agricultural runoff pouring out of the river has doubled in the past few decades.
Unsupported. Agricultural runoff has caused phosphorus levels to double in the past few decades. This doesn’t mean that the runoff itself has doubled in the past few decades.
E
The amount of oxygen in a body of water is in general inversely proportional to the level of phosphorus in that body of water.
Unsupported. It’s true that in this specific region, the water’s oxygen levels have decreased as its phosphorus levels have increased. But this is due to a particular chain of events. We don’t know that oxygen and phosphorus levels are inversely proportional in general.
Summarize Argument: Phenomenon-Hypothesis
The author hypothesizes that drivers feel possessive of their parking spots, and increasingly possessive when other drivers want their parking spots.
Notable Assumptions
The author believes that the drivers took more time leaving their spots when other cars were around because they were possessive of their spots. He therefore assumes there’s not some other factor (i.e. the fact there’s a car nearby as they’re leaving the spot) preventing drivers from leaving their spots as quickly as they would when there aren’t other cars around.
A
The more pressure most drivers feel because others are waiting for them to perform maneuvers with their cars, the less quickly they are able to perform them.
Drivers aren’t possessive when other cars are around. They’re simply feeling pressure, which makes them slow down while leaving their spots.
B
The amount of time drivers spend entering a parking space is not noticeably affected by whether other drivers are waiting for them to do so, nor by whether those other drivers are honking impatiently.
We don’t care what happens when drivers enter a spot. We care what happens while they’re leaving a spot.
C
It is considerably more difficult and time-consuming for a driver to maneuver a car out of a parking space if another car waiting to enter that space is nearby.
This explains why drivers took longer to leave the space than when no cars were waiting, but it doesn’t explain why honking intensified the effect. We need to know why that caused drivers to slow down even more.
D
Parking spaces in shopping mall parking lots are unrepresentative of parking spaces in general with respect to the likelihood that other cars will be waiting to enter them.
We don’t care about how frequently this scenario occurs.
E
Almost any driver leaving a parking space will feel angry at another driver who honks impatiently, and this anger will influence the amount of time spent leaving the space.
Even without the honking, drivers still took longer to leave when another car was waiting for the spot. We need to explain why that is.
Shark teeth are among the most common vertebrate fossils; yet fossilized shark skeletons are much less common—indeed, comparatively rare among fossilized vertebrate skeletons.
"Surprising" Phenomenon
Why are fossils of sharks’ teeth so common while fossils of their skeletons are rare?
Objective
The right answer will be a hypothesis that explains a key difference between the teeth and skeletons of ancient sharks. That difference must result in fossilized teeth being more likely to be found, either because there are actually a higher number of fossilized teeth in the world or else because something makes it easier to discover those tooth fossils.
A
Unlike the bony skeletons of other vertebrates, shark skeletons are composed of cartilage, and teeth and bone are much more likely to fossilize than cartilage is.
This explains a key difference between the teeth and skeletons of sharks. Shark skeletons, which are composed of cartilage, are much less likely to fossilize than shark teeth. Because of this, fossilized shark teeth are more likely to be found than fossilized shark skeletons.
B
The rare fossilized skeletons of sharks that are found are often found in areas other than those in which fossils of shark teeth are plentiful.
This doesn’t explain the difference between shark teeth and shark skeletons or account for why fossilized shark skeletons are so rare. Fossilized shark skeletons and teeth may end up in different areas, but we still don’t know why fossilized shark teeth are more plentiful.
C
Fossils of sharks’ teeth are quite difficult to distinguish from fossils of other kinds of teeth.
The stimulus tells us that shark teeth fossils are common. We can’t assume that those fossils are misidentified just because it’s difficult to distinguish them from fossils of other teeth. Also, we still have no information about why fossilized shark skeletons are so rare.
D
Some species of sharks alive today grow and lose many sets of teeth during their lifetimes.
We can’t assume that something that applies to some shark species alive today also applies to those species that are now fossilized. Also, even if ancient sharks did lose lots of teeth, we still have no explanation for why fossilized shark skeletons are so much more rare.
E
The physical and chemical processes involved in the fossilization of sharks’ teeth are as common as those involved in the fossilization of shark skeletons.
If the fossilization processes of shark teeth and skeletons are equally common, it seems that the fossils should be equally common as well. We need a key difference between the two, not a similarity, in order to explain why tooth fossils are more common than skeleton fossils.
Summary
The author concludes that photographs are interpretations of reality. This is based on the fact that photographers express their own worldviews in their photographs.
Missing Connection
Does expressing one’s own worldview constitute an “interpretation of reality”? It might seem like a reasonable assumption, but it’s still an assumption. It’s not explicitly stated, nor is it something that must be true based purely on the definitions of “expressing a worldview” or “interpretation of reality.” So we’re looking for “Expressing one’s worldview constitutes interpreting reality.”
A
Even representing a subject realistically can involve interpreting that subject.
(A) establishes that a realistic representation “can” involve interpreting the subject. But this doesn’t guarantee that it always constitutes an interpretation of reality. (A) leaves open the possibility that some photos are not interpreting reality, even if other photos “can” involve interpreting reality.
B
To express a worldview is to interpret reality.
The premise establishes that photographs express worldviews. In connection with (B), we can conclude that photographs interpret reality.
C
All visual art expresses the artist’s worldview.
We already know that photos express the photographers’ worldviews. What’s missing is whether such expression constitutes interpreting reality. (C) doesn’t tell us that such expression constitutes interpreting reality.
D
Any interpretation of reality involves the expression of a worldview.
(D) reverses what we’re looking for. We want to know that all expressions of worldviews involve interpretations of reality. But (D) asserts that all interpretations of reality involve expressions of a worldview. This leaves open the possibility that some expressions of worldviews might not involve interpretations of reality.
E
Nonrealistic photographs, like realistic photographs, express the worldviews of the photographers who take them.
We already know that photos express the photographers’ worldviews. What’s missing is whether such expression constitutes interpreting reality. (E) doesn’t tell us that such expression constitutes interpreting reality.
Summarize Argument
The author concludes that the marks are traces of geological processes rather than worms. This is because the tracks were made long before multicellular life existed.
Notable Assumptions
The author believes that the only two things that could’ve made the marks are worms and geological processes. Thus, the author assumes there’s no relevant third factor that could’ve been responsible for the marks.
A
It is sometimes difficult to estimate the precise age of a piece of sandstone.
We don’t need the precise age. The marks were made millions of years before the advent of multicellular animal life.
B
Geological processes left a substantial variety of marks in sandstone more than half a billion years before the earliest known multicellular animal life existed.
This strengthens the author’s argument. If geological processes left a variety of marks, then some of those marks could’ve been the ones that look like they were left by worms.
C
There were some early life forms other than worms that are known to have left marks that are hard to distinguish from those found in the piece of sandstone.
These marks were left well before multicellular life existed. This talks about early life forms “other than worms,” which suggests these life forms were contemporaneous with worms.
D
At the place where the sandstone was found, the only geological processes that are likely to mark sandstone in ways that resemble worm tracks could not have occurred at the time the marks were made.
While worms are out of the question, so are geological processes. There must be some other explanation that the author overlooks.
E
Most scientists knowledgeable about early animal life believe that worms are likely to have been among the earliest forms of multicellular animal life on Earth, but evidence of their earliest existence is scarce because they are composed solely of soft tissue.
These marks were made millions of years before multicellular animal life existed. Regardless of how early worms were relative to other forms of animal life, they were still millions of years too late to leave the marks.
Summary
An organ or body structure is often the only mean of accomplishing a task. It is unsurprising that a type of organ or body structure may evolve at different times in unrelated species. Animals share fundamentally similar needs despite differences in heritage and habitat.
Strongly Supported Conclusions
Different animals may develop similar organs to accomplish the needs they share.
A
will often live in the same environment as other species quite different from themselves
This is unsupported because the stimulus provides no information to predict where different animals will live.
B
will in many instances evolve similar adaptations enabling them to satisfy these needs
This is strongly supported because we are told that sometimes an organ or physical structure is the only way of accomplishing a function. So if different animals have the same functions they need to accomplish, they may develop similar organs to accomplish those functions.
C
will develop adaptations allowing them to satisfy these needs
This is unsupported because although needs may be satisfied through adaptations, answer choice B does a better job of noting that the similarity of needs will likely result in a similarity of adaptations.
D
will resemble other species having different biological needs
This is antisupported because if other species have different biological needs, and needs may be met with unique organs designed for specific functions, species with different needs would likely develop organs that do not resemble each other’s.
E
will all develop eyes or wings as adaptations
This is unsupported because we don’t know that the common needs all animals share would be satisfied by eyes or wings.
Summary
The author concludes that if steel-manufacturing plants could feed the heat they produce into thermo. generators, they would save money by reducing electric bills. Why? Because the process of making steel makes a lot of heat that currently goes to waste. Thermo. generators can convert heat into electricity.
Notable Assumptions
We know that thermo. generators can convert heat into electricity. And we know that there’s a lot of waste head from making steel. If the generators could convert the heat into electricity, electric bills might be reduced. But does that prove there will be overall cost savings? There might be other costs to take into account — costs of installing, running, and maintaining the generators, for example. The author’s assuming that these other costs associated with the thermo. generator would not outweigh the cost savings from reduced electric bills.
A
There is no other means of utilizing the heat produced by the steel-manufacturing process that would be more cost effective than installing thermophotovoltaic generators.
The author never suggested that thermo. generators would be the most cost effective means of using the currently wasted heat. Even if there were more cost effective means, the thermo. generators could still be one way to save money.
B
Using current technology, it would be possible for steel-manufacturing plants to feed the heat they produce into thermophotovoltaic generators in such a way that those generators could convert at least some of that heat into electricity.
The conclusion is based on the hypothetical situation in which the plants could feed heat into thermo. generators. If that’s possible, the author says, then it would save money. But this doesn’t require an assumption that the hypothetical situation is in fact true with current technology. Even if current tech. can’t do it, we can still argue about what would happen IF it were possible.
C
The amount steel-manufacturing plants would save on their electric bills by feeding heat into thermophotovoltaic generators would be sufficient to cover the cost of purchasing and installing those generators.
Necessary, because if it were not true — if the savings on electric bills would NOT be enough to cover the cost of purchasing/installing the generators — then the generators would not result in “saving money.” The savings from electric bills would be offset by the other costs.
D
At least some steel-manufacturing plants rely on electricity as their primary source of energy in the steel-manufacturing process.
Not necessary, because as long as steel plants use electricity at all, the author’s argument can still work. There can still be savings on electric bills, even if electricity is not the primary source of energy for any steel plants.
E
There are at least some steel-manufacturing plants that could greatly reduce their electricity bills only if they used some method of converting wasted heat or other energy from the steel-manufacturing process into electricity.
Summarize Argument: Phenomenon-Hypothesis
The scientists hypothesize that once barn owls learn to locate sounds through their hearing, they stop using their vision to locate sounds. They support this with a study where lenses were placed over baby barn owls' eyes. The owls misjudged sound locations and continued to do so even after they matured and the lenses were removed.
Identify and Describe Flaw
The scientists hypothesize that barn owls stop using their eyes to locate the source of sounds, because the owls in the study continued to misjudge sound locations even after the lenses were removed. But they ignore the alternative hypothesis that the lenses might have permanently damaged these owls’ eyes. In other words, what if the lenses just blinded the owls in the study, making them unable to use their vision to locate sounds even after the lenses were removed?
A
It fails to consider whether the owls’ vision was permanently impaired by their having worn the lenses while immature.
It’s possible that the owls continued to misjudge the source of sounds because their vision was permanently impaired by the lenses, and not because all owls stop using vision to locate sounds once they develop “an auditory scheme” for doing so.
B
It assumes that the sense of sight is equally good in all owls.
The argument is about barn owls, not all owls. Regardless, the scientists never assume that all barn owls have equally good vision. Instead, they draw a conclusion about all barn owls based on a study of barn owls that were given lenses from birth to maturity.
C
It attributes human reasoning processes to a nonhuman organism.
The scientists never argue that the owls use human reasoning. Instead, they hypothesize about the owls’ process of locating sounds.
D
It neglects to consider how similar distorting lenses might affect the behavior of other bird species.
The scientists’ hypothesis is only about how barn owls locate sounds. It doesn’t matter how the lenses might affect other bird species’ behavior.
E
It uses as evidence experimental results that were irrelevant to the conclusion.
The scientists do use experimental results as evidence, but those results are relevant because they’re directly related to the conclusion.
As often now as in the past, newspaper journalists use direct or indirect quotation to report unsupported or false claims made by newsmakers. However, journalists are becoming less likely to openly challenge the veracity of such claims within their articles.
"Surprising" Phenomenon
Journalists still report unsupported or false claims made by newsmakers, but they are now less likely to openly challenge the truth of these claims in their articles.
Objective
Four of the answer choices will provide a hypothesis that explains why journalists today might be less willing or less able to openly challenge the truth of the false or unsupported claims quoted in their articles.
Note that we are looking for the answer choice that does not help to explain the trend in journalism.
A
Newspaper publishers have found that many readers will cancel a subscription simply because a view they take for granted has been disputed by the publication.
This helps to explain the trend in journalism by suggesting that if journalists challenge the false or unsupported claims in their articles, they risk losing readers who believe those claims. Losing readers would also mean losing revenue for the newspaper.
B
The areas of knowledge on which journalists report are growing in specialization and diversity, while journalists themselves are not becoming more broadly knowledgeable.
This helps to explain the trend in journalism. If journalists now cover a wider range of topics without having deep knowledge of them, they may not challenge the false or unsupported claims in their articles because they don’t know if those claims are true or false.
C
Persons supporting controversial views more and more frequently choose to speak only to reporters who seem sympathetic to their views.
This helps to explain the trend in journalism. If journalists only hear from newsmakers whose views they agree with, they are less likely to challenge those views when quoting them in articles.
D
A basic principle of journalism holds that debate over controversial issues draws the attention of the public.
This does not help to explain the trend in journalism. If debate over controversial issues draws public attention and newspapers want public attention, journalists would be more likely to challenge the truth of the false or unsupported claims quoted in their articles.
E
Journalists who challenge the veracity of claims are often criticized for failing their professional obligation to be objective.
This helps to explain the trend in journalism. If journalists who challenge the truth of claims are often criticized, this might make them less likely to continue to openly challenge the truth of the false or unsupported claims quoted in their articles.