Toxicologist: A survey of oil-refinery workers who work with MBTE, an ingredient currently used in some smog-reducing gasolines, found an alarming incidence of complaints about headaches, fatigue, and shortness of breath. Since gasoline containing MBTE will soon be widely used, we can expect an increased incidence of headaches, fatigue, and shortness of breath.

Summarize Argument
The toxicologist concludes that headaches, fatigue, and shortness of breath will soon rise. This is because gas with MBTE will soon be widely used, and people who work with MBTE report increased rates of the aforementioned symptoms.

Notable Assumptions
The toxicologist assumes that the oil refinery workers experienced headaches, fatigue, and shortness of breath because of the MBTE, and not because of some other substance they worked with. He thus believes that oil refinery workers who don’t work with MBTE wouldn’t experience the same symptoms, at least not for the same reason. The toxicologist also assumes that there will be no difference between the MBTE gasoline dealt with in oil refineries and the MBTE gasoline ordinary people will use.

A
Most oil-refinery workers who do not work with MBTE do not have serious health problems involving headaches, fatigue, and shortness of breath.
This strengthens the causal relationship between MBTE and the symptoms by ruling out an alternate cause. If all oil refinery workers experienced headaches, fatigue, and shortness of breath, then MBTW couldn’t be identified as a cause.
B
Headaches, fatigue, and shortness of breath are among the symptoms of several medical conditions that are potentially serious threats to public health.
We don’t care about medical conditions that don’t stem from MBTE. This just tells us that people suffering from various conditions experience the same symptoms brought on by MBTE exposure.
C
Since the time when gasoline containing MBTE was first introduced in a few metropolitan areas, those areas reported an increase in the number of complaints about headaches, fatigue, and shortness of breath.
MBTE has already led to an increase in headaches, fatigue, and shortness of breath. This suggests that MBTE isn’t just dangerous in a refinery setting.
D
Regions in which only gasoline containing MBTE is used have a much greater incidence of headaches, fatigue, and shortness of breath than do similar regions in which only MBTE-free gasoline is used.
Compared with MBTE-free gasoline, MBTE gasoline is correlated with headaches, fatigue, and shortness of breath. This strengthens the author’s link between MBTE and the symptoms.
E
The oil-refinery workers surveyed were carefully selected to be representative of the broader population in their medical histories prior to exposure to MBTE, as well as in other relevant respects.
The survey wasn’t skewed. This strengthens the author’s use of the survey as evidence.

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Journalist: Obviously, though some animals are purely carnivorous, none would survive without plants. But the dependence is mutual. Many plant species would never have come to be had there been no animals to pollinate, fertilize, and broadcast their seeds. Also, plants’ photosynthetic activity would deplete the carbon dioxide in Earth’s atmosphere were it not constantly being replenished by the exhalation of animals, engine fumes, and smoke from fires, many set by human beings.

Summarize Argument
Plants depend on animals for their survival; it’s not just animals that depend on plants. This is because animals play an essential role in ensuring the survival and spread of plant species by pollinating, fertilizing, and broadcasting seeds. Further, animals make sure there is continually enough carbon dioxide in the atmosphere for plants to undergo photosynthesis. This is achieved not only when animals exhale, but also when humans emit carbon dioxide through fires and fumes from machines.

Identify Conclusion
The conclusion is that plants also depend on animals for their survival: “The dependence is mutual.”

A
The photosynthetic activity of plants is necessary for animal life, but animal life is also necessary for the occurrence of photosynthesis in plants.
The role of photosynthesis is cited as a premise for the conclusion that animals and plants both depend on each other. Photosynthesis is just an example that demonstrates the mutual dependence; the conclusion is not about photosynthesis.
B
Some purely carnivorous animals would not survive without plants.
Our conclusion is about the mutual dependence between plants (in general) and animals (in general), not the dependence of a subset of animals (in this answer, the subset is “purely carnivorous animals”) on plants.
C
The chemical composition of Earth and its atmosphere depends, at least to some extent, on the existence and activities of the animals that populate Earth.
The conclusion of the argument does not involve the chemical composition of Earth and its atmosphere. One specific aspect of the chemical composition (the balance of carbon dioxide in the atmosphere) is referenced as a premise.
D
Human activity is part of what prevents plants from depleting the oxygen in Earth’s atmosphere on which plants and animals alike depend.
This is part of a premise. This answer provides support for the conclusion that plants also depend on animals.
E
Just as animals are dependent on plants for their survival, plants are dependent on animals for theirs.
This is the conclusion that the rest of the argument sets out to support. The journalist is trying to convince the reader of the mutual dependence between plants and animals; every other part of the argument supports this idea.

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Ms. Smith: I am upset that my son’s entire class lost two days of recess because some of the children were throwing raisins in the cafeteria. He was not throwing raisins, and it was clear to everyone just who the culprits were.

Principal: I’m sorry you’re upset, Ms. Smith, but your son’s situation is like being caught in a traffic jam caused by an accident. People who aren’t involved in the accident nevertheless have to suffer by sitting there in the middle of it.

Summary

Ms. Smith’s son’s class lost two days of recess.

The class lost recess because some of the children were throwing raisins.

Ms. Smith believes her son wasn’t throwing raisins.

Ms. Smith believes everyone knows who was throwing raisins.

Ms. Smith believes that it’s unfair for her son to lose two days of recess because of the raisin incident.

The principal believes that Ms. Smith’s son is collateral damage in the punishment over the raisin-throwing.

Very Strongly Supported Conclusions

The principal believes it’s possible that Ms. Smith’s son did not throw raisins.

The principal believes that it is sometimes acceptable for a person to suffer as a result of another person’s actions.

A
many children were throwing raisins in the cafeteria

Unsupported. The principal says nothing about how many or few children were throwing raisins in the cafeteria.

B
Ms. Smith’s son might not have thrown raisins in the cafeteria

Very strongly supported. The principal’s analogy likens Ms. Smith’s son to people who didn’t cause the traffic jam they’re stuck in. This suggests that the principal believes Ms. Smith’s son might not have caused the incident that led his class to lose recess.

C
after an accident the resulting traffic jams are generally caused by police activity

Unsupported. The principal does not mention police activity or give any reason to believe that she thinks police generally cause traffic jams after accidents.

D
Ms. Smith’s son knows who it was that threw raisins in the cafeteria

Unsupported. The principal doesn’t comment on whether or not anyone knows who threw the raisins. Rather, Ms. Smith is the one who believes that “everyone” knew who the culprits were.

E
losing two days of recess will deter future disruptions

Unsupported. The principal doesn’t comment on the motivations behind the decision to take away two days of recess. Maybe she thinks it will deter future disruptions, or maybe it’s just generally meant to punish the students.


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