Summarize Argument: Phenomenon-Hypothesis
The conservationists hypothesize that non-native predators are endangering ringtail opossums, instead of a food scarcity. Why? Because non-native foxes killed 75 percent of a particular group of opossums that had been rehabilitated and returned to the wild.
Notable Assumptions
The conservationists assume the group of opossums raised in captivity died in a way typical of the general ringtail opossum population. This means assuming the group was large enough and diverse enough to be representative of ringtail opossums in Australia. They also assume a food scarcity would not make ringtail opossums any more vulnerable to predators and that their endangerment cannot be explained by anything except non-native predation.
A
There are fewer non-native predator species that prey on the ringtail opossum than there are native species that prey on the ringtail opossum.
This doesn’t mean non-native predators pose a larger threat. If anything, it suggests the total number of opossums killed by native predators could be greater than the number killed by non-native predators, which would weaken the argument.
B
Foxes, which were introduced into Australia over 200 years ago, adapted to the Australian climate less successfully than did some other foreign species.
This is irrelevant. It doesn’t mean other non-native species pose an even larger threat to ringtail opossums than foxes—there’s no indication those other species even prey on foxes.
C
The ringtail opossums that were raised in captivity were fed a diet similar to that which ringtail opossums typically eat in the wild.
This suggests the opossums killed had diets that were typical of wild opossums, not that their cause of death was typical. It doesn’t disfavor the leading alternative hypothesis, a food scarcity, because it doesn’t imply the opossums killed were able to find food in the wild.
D
Few of the species that compete with the ringtail opossum for food sources are native to Australia.
This is irrelevant. The conservationists explicitly blame non-native predators for the ringtail opossum’s endangerment, not species that compete with them for food.
E
Ringtail opossums that grow to adulthood in the wild defend themselves against foxes no more successfully than do ringtail opossums raised in captivity.
This rules out an alternative explanation for the opossums’ deaths: that the opossums raised in captivity were killed by foxes in large numbers because they were unusually bad at protecting themselves.
Summarize Argument: Counter-Position
The economist concludes that the ozone layer has a calculable monetary value—i.e. the amount of money we would be willing to spend to protect it. This is supported by the claim that we wouldn’t spend all of the world’s economic resources to protect the ozone layer. This leads to the sub-conclusion that there must be an upper limit to how much the ozone layer is worth.
Identify and Describe Flaw
The economist concludes that a certain value is calculable because there is an upper limit to that value. However, even if there is an upper limit to the ozone layer’s value, that still doesn’t establish that the exact monetary value of the ozone layer can be calculated.
A
uses evidence that the monetary value of a particular natural resource is less than a certain amount in order to establish that the monetary value of any natural resource is less than that amount
The economist never discusses natural resources other than the ozone layer, nor makes any claims about other natural resources.
B
presupposes that the ozone layer should not be protected and then argues to that claim as a conclusion
The economist just doesn’t conclude that the ozone layer shouldn’t be protected. The conclusion here is that the ozone layer has a calculable monetary value, not whether or not we should protect it.
C
takes advantage of an ambiguity in the term “value” to deflect the environmentalists’ charge
There is no ambiguity in how the term “value” is used here, by either the economist or the environmentalists. Everyone involved uses “value” to mean “monetary value” and nothing else.
D
gives no reason for thinking that merely establishing an upper limit on a certain monetary value would allow the calculation of that monetary value
The economist establishes that the ozone layer’s monetary value has an upper limit, but doesn’t give us any reason to think that that its exact monetary value can be calculated from there.
E
does not directly address the argument of the environmentalists
The economist does directly address the environmentalists’ argument: the environmentalists claim that the ozone layer does not have a calculable monetary value, and the economist argues directly against that claim.
Summary
Zoos are both educational and entertaining. However, removing animals from their natural habitats to populate the earliest zoos caused some species’ populations to reduce and endangered their survival. Today, most new zoo animals are bred from captive breeding programs. These programs make possible efforts to restore populations of endangered species in the wild.
Strongly Supported Conclusions
At least some animals bred through captive breeding programs are of an endangered species.
A
Zoos have played an essential role in educating the public about endangered species.
We don’t know whether zoos have played an essential role or not. We only know that zoos have served as an educational resource. Additionally, we don’t know whether these educational resources were specific to endangered species.
B
Some specimens of endangered species are born and bred in zoos.
If captive breeding programs make reestablishing endangered species in the wild possible, it must be that zoos are breeding at least some species of endangered animals.
C
No zoos exploit wild animals or endanger the survival of species.
We don’t know whether there isn’t any zoo that exploits wild animals. We know that most new zoo animals are obtained through breeding programs, but not all of them.
D
Nearly all of the animals in zoos today were born in captivity.
We don’t know whether nearly all zoo animals were born in captivity. We know that most new zoo animals are obtained through breeding programs, but “most” could mean as little as 51 percent of animals.
E
The main purpose of zoos has shifted from entertainment to education.
We don’t know what would be the main purpose of zoos. We only know that they have served as educational resources and as entertainment.
Summary
Special cotton from green/brown fibers havae been around since 1930s. Only recently, this special cotton became commercially feasible when a long-fibered kind that can be spun by machine came about. This long-fibered kind doesn’t need to be dyed, which is why processing plants don’t need to spend money on dyeing. In addition, since the long-fibered variety doesn’t need to use dyes, plants don’t need to get rid of leftover dye from processing, which avoids some ecological damage.
Very Strongly Supported Conclusions
There’s no obvious conclusion to draw from these facts. I’d go into the answers thinking, “There are at least some advantages to the long-fibered variety of cotton from green/brown fibers over the non-long-fibered variety of that cotton.” But the correct answer could be unexpected.
A
It is ecologically safer to process long-fibered cotton than short-fibered cotton.
We know that the long-fibered green/brown cotton doesn’t have a certain ecological risk (because it doesn’t require dyes). But this doesn’t extend to long-fibered cotton that isn’t green/brown. We don’t know about ecological risks of other kinds of long cotton.
B
Green and brown cottons that can be spun only by hand are not commercially viable.
Strongly supported, because the green/brown cotton “only recently” became commercially feasible, and this happened after a variety that could be machine-spun “finally” came about. This suggests that before a machine-spun version came about, it wasn’t commercially viable.
C
Hand-spun cotton is more ecologically safe than machine-spun cotton.
We don’t get a comparison concerning ecological damage between machine-spun vs. hand-spun cotton. All we know about ecological risk is that if you don’t have to use dyes, you avoid at least one ecological risk.
D
Short-fibered regular cottons are economically competitive with synthetic fabrics.
We don’t get any comparison between short-fibered cottons and synthetic fabrics.
E
Garments made of green and brown cottons are less expensive than garments made of regular cotton.
We know that processing plants don’t need to spend on dyes for creating green/brown cotton. This doesn’t suggest that clothes from green/brown cotton are less expensive, however. There are many other costs that go into clothing; we can’t go from the lack of one specific cost with respect to the cotton to a claim about overall cost of clothing from the green/brown cotton compared to other clothing.