Summarize Argument
The author concludes that there must be a lake of liquid water between Enceladus’s rocky core and icy surface. This is because a space probe discovered something denser than ice between the core and the surface, and that denser substance can only be liquid water.
Identify Conclusion
The conclusion is the assertion that there’s a lake of liquid water between Enceladus’s rocky core and icy surface: “Between these two layers, there must be a lake of liquid water.”
A
Saturn’s moon Enceladus has a rocky core and an icy surface.
This is context. The author’s conclusion concerns what must be in between those two layers.
B
There must be a lake of liquid water between the rocky core and the icy surface of Enceladus.
This is a restatement of the second sentence, which is the conclusion.
C
The Cassini space probe was used to measure the density of Enceladus.
This is part of the support. The author concludes that there must be a lake of liquid water based on what this probe found.
D
Density measurements reveal something denser than ice between the core and surface of Enceladus.
This is part of the support. The author concludes that there must be a lake of liquid water based on these measurements.
E
Anything denser than ice between the core and surface of Enceladus would have to be liquid water.
This is part of the support. Because the denser substance could only be water, the author concludes that a lake of liquid water must exist between the rocky core and icy surface.
Summary
Rodents are small mammals that have chisel-like incisor teeth. Most individual mammals in North America are rodents, even though most mammal species in North America are not rodents.
Strongly Supported Conclusions
In North America, rodent species usually have more individual members than other species of mammals.
A
Most species of North American mammals have chisel-like incisor teeth.
This answer is unsupported. The stimulus only tells us of one example of a species of mammal that has chisel-like incisor teeth. To say that most mammal species have these teeth is too extreme.
B
In North America, rodent species tend to have more individual members than other species of mammals have.
This answer is strongly supported. We know from the stimulus that most individual mammals in North America are rodents. Therefore, rodent species tend to have more individual member than mammal species that are not rodents.
C
Most species of mammals that have chisel-like incisor teeth can be found in North America.
This answer is unsupported. The stimulus only tells us of one example of a species of mammal in North America that has chisel-like incisor teeth. We cannot assume that there are other species with similar teeth from the stimulus.
D
Of the mammal species in North America, the one with the most individual members is a species of rodent.
This answer is unsupported. We don’t know from the stimulus how many species of rodent exist, and we don’t know how many individual members exist within each potential species of rodent to make this claim.
E
Most nonrodent mammal species can be found in North America.
This answer is unsupported. We don’t have any information in the stimulus about mammal species existing outside of North America to make this comparison.
"Surprising" Phenomenon
Toning shoes don’t exercise leg muscles more than regular shoes, yet most people who switch to toning shoes experience a strengthening of their leg muscles.
Objective
The correct answer will be a hypothesis that explains a key difference between toning shoes and regular shoes, beyond the actual exercise the shoes afford. This difference likely rests in who wears the shoes. People may, for example, experience a strengthening of their leg muscles after switching to toning shoes because they’re making a concerted effort to get exercise.
A
Toning shoes strengthen small underused muscles in the feet and ankles.
We’re concerned with how major leg muscles are strengthened.
B
Muscles in the leg adapt to the rounded shape of toning shoes almost immediately.
This reinforces the idea that toning shoes provide no exercise benefit. We need to know why people who switch to them get a benefit, anway.
C
Many people find toning shoes especially comfortable and walk more as a result.
True, toning shoes don’t have any real exercise advantage over regular shoes. But people who switch to toning shoes end up walking more, which certainly exercises their leg muscles. This explains how they get a benefit from toning shoes.
D
There is little evidence that toning shoes cause injuries to their wearers.
Our stimulus says nothing about injuries. We need to know why people who switch to toning shoes get a benefit.
E
Shoes that strengthen the major leg muscles are more marketable than ordinary shoes.
Toning shoes don’t themselves strengthen the major leg muscles.
"Surprising" Phenomenon
Despite having high radiation levels, wildlife populations around Chernobyl have expanded rapidly.
Objective
The right answer will be a hypothesis that explains why wildlife populations expanded after the Chernobyl accident, despite the high levels of radiation wildlife populations have. This explanation must result in population increases being a likely outcome given the circumstances after the accident. These circumstances must outweigh the negative effects of the radiation.
A
Animals that did not arrive in the area around the Chernobyl nuclear plant until after the accident still developed high levels of radiation in their muscles and bones.
We need to know why these animals were still able to proliferate despite high levels of radiation. This doesn’t offer an explanation for that peculiar phenomenon.
B
Some of the species that inhabit the region are migratory and so only live in the region for part of the year, limiting their exposure to the radiation.
The stimulus tells us that wildlife populations generally have high levels of radiation. We’re not interested in a few outliers.
C
The region affected by the release of radiation is very large, encompassing 1,800 square miles (4,660 square kilometers).
All this says is that lots of wildlife populations were likely affected by the radiation. We need to know why their populations expanded.
D
While some of the radioactive chemicals released by the accident depress fertility in local birds, others do not.
Like (B), “some” signifies an outlier. We need to know why wildlife populations in general expanded despite having high levels of radiation.
E
The threat of radiation poisoning drove people out of the area, which opened up new habitat for wildlife and eliminated the danger from hunters.
Though radiation may be a threat in itself, wildlife populations were generally safer after Chernobyl. For one thing, they had a larger habitat since humans had to leave. For another, there were no more hunters around. This explains why their populations increased.