"Surprising" Phenomenon
Prehistoric birds had growth rings suggesting they were cold-blooded animals, but dense blood vessels suggesting they were warm-blooded animals.
Objective
A hypothesis resolving this dispute must state a key similarity or difference between prehistoric birds and either cold-blooded or warm-blooded animals. It must allow for prehistoric birds to have both growth rings and dense blood vessels while being exclusively either cold-blooded or warm-blooded.
A
Some modern warm-blooded species other than birds have been shown to have descended from cold-blooded species.
This does not favor either possibility. Though other warm-blooded species descended from cold-blooded species, it is possible warm-blooded birds descended from warm-blooded prehistoric birds.
B
Having growth rings is not the only physical trait of cold-blooded species.
This is irrelevant information that does not favor either possibility. It is not stated whether prehistoric birds possessed any other traits of cold-blooded species.
C
Modern birds did not evolve from prehistoric species of birds.
In dispute is whether prehistoric birds were warm-blooded or cold-blooded, regardless of whether they were ancestors of modern birds. Both studies draw conclusions about prehistoric birds explicitly, so this does not favor either possibility.
D
Dense blood vessels are not found in all warm-blooded species.
This gets the desired relationship backward. It states that some warm-blooded species do not have dense blood vessels, but admits the possibility that all species with dense blood vessels are warm-blooded.
E
In some cold-blooded species the gene that is responsible for growth rings is also responsible for dense blood vessels.
This suggests prehistoric birds were cold-blooded. It implies that dense blood vessels are not necessarily evidence of warm-bloodedness, especially among animals with growth rings, calling into question the conclusion of the second study.
Summarize Argument
The author thinks that the government should spend more on preventing chemical spills, rather than focusing primarily on cleaning them up. Why should we believe this? First, the current strategy is slow and is not keeping up with new spills; this shows us that something needs to change. Second, the author tells us that prevention is more effective than cleanup; this indicates what the change should be. Finally, we learn that the current annual spending on prevention is less than even one cleanup site costs per year; this highlights the urgency of the situation. All together, everything in the argument leads to the conclusion that we should spend more on prevention rather than cleanup.
Identify Argument Part
The claim about how the government’s budget should be redirected is the main conclusion of the argument.
A
It represents an unsupported speculation.
The proposal of redirecting the budget is not unsupported; in fact, everything else in the argument supports it.
B
It both supports another claim in the argument and is supported by others.
The proposal of redirecting the budget does not support anything else in the argument. It receives support, but it’s the main conclusion, so the support ends there.
C
It is the claim that the argument as a whole is structured to support.
This correctly describes that the proposal of redirecting the budget is the author’s main conclusion, and is supported by everything else in the argument.
D
It is a presupposition on which the argument is explicitly based.
The author never makes an explicit presupposition, so this wouldn’t be true of any part of the argument. Also, the claim about redirecting the budget is supported by other claims, not assumed (or presupposed).
E
It presents an objection to another proposal mentioned in the argument.
There is no other proposal mentioned in the argument. The author is arguing for a change from the current policy, but there are no competing views about what the change should be.