Summarize Argument: Phenomenon-Hypothesis
The argument concludes that a metabolic quirk of the brain is likely to be the reason that many different human hormones can raise the concentration of glucose in the blood. To prove this, the argument cites the fact that the brain can only use glucose for energy, while most other cells can produce energy from fats and proteins. Because glucose is the brain’s exclusive energy source, low levels of glucose in the blood can be very dangerous for brain cells, potentially leading to unconsciousness and death.
Identify Conclusion
The conclusion tells us the reason why different human hormones can raise blood glucose on their own: “The reason for this is probably a metabolic quirk of the brain.”
A
Each of many different human hormones can by itself raise blood glucose levels.
This is the phenomenon that our conclusion sets out to explain. The argument does not provide support for this claim; we accept it upfront, which tells us that this is not the conclusion. The hypothesis that this phenomenon is caused by a metabolic quirk is the main conclusion.
B
The reason that many different hormones can each independently raise blood glucose levels is probably a metabolic quirk of the brain.
This is the claim that the rest of the argument works to prove, which makes it the main conclusion. This statement tells us the cause of the phenomenon introduced in the argument; the rest of the argument provides support for this causal reasoning.
C
Although most human cells can produce energy from fats and proteins, brain cells can produce energy only from glucose.
This claim supports the sub-conclusion that a low level of blood glucose is dangerous for the brain. This answer is a premise, not the main conclusion.
D
If blood glucose levels fall too low, then brain cells starve, resulting in loss of consciousness and death.
This is a sub-conclusion that helps support the main conclusion, which is that a metabolic quirk is the reason many different hormones can raise blood glucose levels. This answer tells us why it is so important for the body to be able to maintain healthy blood glucose levels.
E
The reason brain cells starve if deprived of glucose is that they can produce energy only from glucose.
This statement references the sub-conclusion, but adds causal reasoning into the sub-conclusion. This is not the main conclusion that the entire argument works to support.
Human resources director: While only some recent university graduates consider work environment an important factor in choosing a job, they all consider salary an important factor. Further, whereas the only workers who consider stress level an important factor in choosing a job are a few veteran employees, every recent university graduate considers vacation policy an important factor.
Summary
Every recent university graduate considers salary an important factor in choosing a job. Some recent university graduates consider work environment an important factor. All recent graduates consider vacation policy an important factor. The only workers who consider stress level an important factor are a few veteran employees.
Notable Valid Inferences
Some people who consider work environment an important factor also consider vacation policy as an important factor.
Some people who consider work environment an important factor also consider salary as an important factor.
Some people who consider salary an important factor also consider vacation policy an important factor.
A
All people who consider work environment an important factor in choosing a job also consider salary an important factor.
Could be false. We can never infer an “all” statement between conditions with a sufficient condition in common. We can only infer “some” statements.
B
At least some people who consider work environment an important factor in choosing a job consider vacation policy an important factor as well.
Must be true. As shown below, we can combine claims that some recent graduates consider work environment important and that all recent graduates consider vacation policy important. We can always infer a “some” statement between conditions with a sufficient condition in common. 
C
At least some veteran employees do not consider work environment an important factor in choosing a job.
Could be false. We only know that some veteran employees are the only workers that consider stress level important. We cannot infer anything else about these veteran employees. As shown on our diagram, there are no other conditional statements attached to this condition.
D
All people who consider vacation policy an important factor in choosing a job also consider salary an important factor.
Could be false. We can never infer an “all” statement between conditions with a sufficient condition in common. We can only infer “some” statements.
E
No one for whom salary is an important factor in choosing a job also considers stress level an important factor.
Could be false. We can never infer an “all” statement between conditions with a sufficient condition in common. We can only infer “some” statements.
Note: The video marks Question #2 as C, when the answer is in fact D. J.Y. miscounted in the video.
Summarize Argument: Phenomenon-Hypothesis
In households that regularly used for the past several years an insect trap consisting of pesticide mixed with glucose, the trap is much less effective today. The author hypothesizes that this is because successive generations of insects developed a resistance to the pesticide in the traps.
Notable Assumptions
The author assumes there isn’t another cause for the decreased effectiveness of the traps.
A
In households where the traps have been used regularly, the proportion of insect pests that have a natural aversion to eating glucose has increased with each successive generation.
This provides an alternate explanation for the decreased effectiveness of the traps. The glucose in the trap is not as attractive anymore, which means fewer insects enter the traps. This results in decreased effectiveness, even if the insects aren’t resistant to the pesticide.
B
Even when only a few individuals out of an entire generation of insects survive the effects of a pesticide, the offspring of those individuals are usually resistant to that pesticide.
If anything, this answer supports the author’s theory by showing resistance can develop in offspring even if one generation is almost entirely wiped out.
C
After eating glucose mixed with the pesticide, insects that live in households that do not use the trap tend to die in greater numbers than do insects from households where the traps have been used regularly.
If anything, this could support the author’s theory by showing that in households where insects haven’t had the chance to build up resistance, the trap is more effective than in households that have used the trap for several years.
D
After the manufacturer of the traps increased the concentration of the pesticide used in the traps, the traps were no more effective in eliminating household insect pests than were the original traps.
This is consistent with the author’s hypothesis. Increased concentration of the pesticide should make the trap more effective. Just because the traps didn’t become more effective than the original doesn’t mean they didn’t become more effective.
E
The kind of glucose used to bait the traps is one of several different kinds of glucose that occur naturally.
The fact the glucose occurs naturally doesn’t have any impact. Does natural glucose have anything to do with the traps’ decreased effectiveness? We have no reason to think so.
Summarize Argument: Counter-Position
The author’s conclusion rejects the view of biologists who believe that the capacity for flight first developed in marine reptiles. Those biologists, with whom the author disagrees, support their claim with the theory that feathers developed from scales. To support his rejection of these biologists, the author uses the example of bats, which fly and have no scales, and non-marine reptiles that have scales. These examples cast doubt on the view that marine reptiles first developed the capacity for flight.
In the last two sentences of the stimulus, the author actually introduces a completely new argument! The discussion in the last two sentences is not relevant for our understanding of the author’s perspective.
In the last two sentences of the stimulus, the author actually introduces a completely new argument! The discussion in the last two sentences is not relevant for our understanding of the author’s perspective.
Identify Argument Part
The claim in the question stem supports the author’s rejection of the view that flight first developed in marine reptiles.
A
It is cited as evidence against the claim that the capacity for flight first developed in marine reptiles.
The claim in the question stem is a premise that supports the author’s conclusion, which is that it is not true that the capacity for flight first developed in marine reptiles. (A) encapsulates this.
B
It is cited as evidence against the claim that the capacity for flight first developed in land-dwelling animals.
The second (irrelevant) argument makes a claim that it is less likely that land-dwelling reptiles’ limbs developed into wings. (B) includes an imprecise reference to this second argument; the claim in the question stem has no relationship with this second argument.
C
It is cited as evidence against the claim that the capacity for flight first developed in tree-dwelling reptiles.
The claim in the question stem does has no relationship to the claim that flight first developed in tree-dwelling animals; instead, the claim in the question stem is used to reject the claim about flight and marine animals.
D
It weakens the claim that tree-dwelling reptiles were the first kind of reptile to develop the capacity for flight.
The claim in the question stem has no relationship to the claim that flight first developed in tree-dwelling animals; instead, the claim in the question stem is used to reject the claim about flight and marine animals.
E
It corroborates the observation that some mammals without scales, such as bats, developed the capacity to fly.
The claim in the question stem works together with the observation that some mammals without scales can fly; these two claims don’t support each other, but they work together to support the main conclusion.