Henry: Engines powered by electricity from batteries cause less pollution than internal combustion engines. Therefore, to reduce urban pollution, we should replace standard automobiles with battery-powered vehicles.

Umit: I disagree. Battery-powered vehicles have very short ranges and must be recharged often. Their widespread use would create a greater demand for electricity generated by power plants, which are themselves a major source of pollution.

Summarize Argument
Umit concludes that we should not replace standard cars with battery-powered cars in order to reduce urban pollution. This is because the widespread use of battery-powered cars would create a greater demand for electricity from power plants, and power plants are a major source of pollution.

Notable Assumptions
Umit assumes that the pollution produced by power plants would affect urban areas (as opposed to affecting only non-urban areas). Umit also assumes that the decrease in urban pollution resulting from switching to battery-powered cars would not outweigh whatever increase in urban pollution is caused by the increased use of power plants.

A
Pollution caused by power plants is generally confined to a small number of locations a significant distance from major cities.
This provides a reason to think that the pollution from power plants would not necessarily affect urban areas. Thus, Umit’s point about pollution from power plants does not necessarily show that battery-powered cars can’t reduce urban pollution.
B
The increased air pollution resulting from a greater demand for electricity would be offset by the reduction in air pollution emitted by electric vehicles.
Even if the increased pollution from electricity demand would be offset by decreased pollution from electric cars, that just means we’re back to the same level of pollution as before. This doesn’t undermine Umit’s point, which is that electric cars won’t decrease urban pollution.
C
Electric motors could be restricted to lighter vehicles such as compact cars, which have smaller batteries and therefore require less power to charge than do the larger batteries needed to power larger vehicles.
Even if electric cars could be limited to smaller batteries, that doesn’t change the fact that widespread use of electric cars would create a greater demand for electricity from power plants.
D
Hybrid vehicles using both electric and gasoline power moderate the increased demand for electricity produced by power plants.
The argument concerns widespread use of battery-powered vehicles. Hybrid vehicles are a different kind of vehicle and don’t impact what would happen if non-hybrid electrics become widespread.
E
Most power plants are currently operating well below capacity and could therefore accommodate the increased demand for electricity.
The issue is not whether the power plants could produce enough electricity. It’s about the pollution produced from the power plants. If anything, (E) might strengthen by showing that power plants have the capacity to make more electricity and thus pollute.

Further Explanation

Henry says that electric engines (cars) pollute less than combustion engines. Therefore, switching from regular cars to electric cars would reduce urban pollution.

This isn't a terrible argument. Car engines are a major contribution to pollution. But, Henry hasn't given an exhaustive (hehe) account of the situation. What if the production of electric engines is way more polluting than the production combustion engines? Sure using electric engines is less pollution but you gotta make them in the first place and that could tip the scales.

Umit doesn't go there, though he could have. He brings up another consideration that Henry overlooked. He reminds us that electric engines run on batteries that need charging. Charging all those batteries places greater demand on power plants which then will generate more pollution as a result.

Okay, yeah, that's a good point Umit! You did a good weakening on Henry's argument by pointing out something Henry overlooked (i.e. assumed wasn't an issue). Henry, batteries don't power themselves okay? You gotta charge them you dodo!

Alright, so now we have to do another 180 and weaken Umit's argument. We have to see that Umit assumed that the extra pollution generated by the power plants is relevant. (A) gives us a reason to think that it's not relevant. If it's true that power plants are not near major cities, then does their pollution even matter? Henry was only concerned about urban pollution after all, not pollution in the entire country or on the whole planet. (A) may as well have told us that these power plants are on Mars.

(B) is an attractive trap. It says that the additional units of pollution from the power plants would be "offset" by the decreased units of pollution from the electric engine cars. Okay, "offset" by how much? Entirely offset? Or just somewhat offset? We're not sure. So it could be on a range anywhere from entirely offset to just somewhat offset. But anywhere on that range is bad for Henry. Even if it's entirely offset, then that just means switching to electric cars is no better than not switching in the first place. Henry actually needs switching to electric cars to be better for urban pollution. Not just neutral.

What (B) needed to say is that the additional additional units of pollution from the power plants is only a tiny fraction of the total decreased units of pollution from the electric engine cars. In other words, power plants are generating +1 unit of pollution but electric cars are saving -10 units of pollution. That would help Henry and hurt Umit.


77 comments

Since mosquito larvae are aquatic, outbreaks of mosquito-borne diseases typically increase after extended periods of wet weather. An exception to this generalization, however, occurs in areas where mosquitoes breed primarily in wetland habitats. In these areas, outbreaks of mosquito-borne diseases are worse after periods of drought.

"Surprising" Phenomenon
Mosquito-borne disease outbreaks typically increase after extended periods of wet weather, but in areas where mosquitoes breed primarily in wetland habitats, there tend to be more outbreaks after droughts.

Objective
The right answer will be a hypothesis that describes a key difference between areas where mosquitoes breed primarily in wetland habitats and areas where mosquitoes breed primarily in other types of environments. That difference must explain why droughts create improved conditions for mosquito-borne disease in areas where breeding occurs in wetland habitats. This difference might relate to humans’ susceptibility to disease, mosquitoes’ disease carriage abilities, or mosquito birthrates under drought conditions in these areas.

A
The use of insecticides is typically prohibited in wetland habitats.
This has nothing to do with droughts or wet periods—presumably, insecticides are prohibited regardless of weather conditions, so (A) doesn’t help explain the increased disease outbreaks that follow droughts in wetland habitats.
B
Human populations tend to be sparse in areas near wetland habitats.
This has nothing to do with droughts or wet periods, so it doesn’t help explain the increased disease outbreaks that follow droughts in wetland habitats.
C
Wetland habitats contain numerous aquatic insects that prey on mosquito larvae.
If wetland habitats contain aquatic insects that eat mosquito larvae, it makes sense that periods of drought lead to more cases of mosquito-borne disease. These aquatic predators die or are weakend during droughts, allowing more larvae to hatch and grow into diseased mosquitoes.
D
Wetland habitats host a wider variety of mosquito species than do other areas where mosquitoes breed.
This has nothing to do with droughts or wet periods, so it doesn’t help explain the increased disease outbreaks that follow droughts in wetland habitats.
E
Periods of drought in wetland habitats create conditions conducive to the emergence of new plant growth.
We have no information about how new plant growth might or might not impact incidences of mosquito-borne disease, so this answer choice doesn’t help resolve the discrepancy at hand.

21 comments

Automobile executive: Our critics say that the communications devices installed in our automobiles are dangerously distracting to drivers. But these critics are wrong. Drivers who want to use communications devices are going to use them regardless. Our devices are easier for drivers to use, and hence they are safer.

Summarize Argument: Counter-Position
The executive concludes that critics are wrong about her communications devices being dangerously distracting. She supports this by saying that drivers who want to use communications devices will do so regardless, and that these devices are safer because they are easier to use.

Identify and Describe Flaw
The executive makes the unwarranted assumption that the devices are safer just because they're easier to use. But even if they are safer than other devices, she still doesn't address the critics' concern that they are dangerously distracting, nor does she give any reason to believe that they are not dangerously distracting. The fact that they're easier to use and that drivers will use them anyway doesn't change the fact that they might still be dangerously distracting.

A
attempts to apply a general principle to a situation to which that principle is not applicable
The executive doesn’t attempt to apply any principle at all. She also doesn’t wrongly apply a generalization to a specific situation. Instead, she draws a conclusion about the communications devices based on premises that are also about the communications devices.
B
fails to address the substantive point of the criticism that it is responding to
The executive fails to address the critics’ main point: that the communications devices are dangerously distracting. Just because they're easier to use and drivers will use them anyway doesn't change the fact that they might still be dangerously distracting.
C
treats a condition that is necessary to establish its conclusion as one that is sufficient to establish that conclusion
This is the cookie-cutter flaw of confusing necessary and sufficient conditions. The executive doesn’t make this mistake; her argument doesn’t rely on conditional logic. Instead, she counters the critics’ position without actually addressing their criticism.
D
presumes, without providing justification, that all communications devices are the same with respect to driver distraction
Actually, the executive explicitly claims that her communications devices are safer with respect to driver distraction. She doesn’t assume that all devices are the same.
E
is based on premises that presume the truth of the argument’s conclusion
This is the cookie-cutter flaw of circular reasoning. The executive doesn’t make this mistake. Her premises may not support her conclusion well, but they are distinct from her conclusion.

9 comments

Carrillo: Using the number of existing primate species, along with measures of the genetic diversity among these primates and among the extinct primate species, our statistical model strongly supports the conclusion that the first primate developed around 81.5 million years ago.

Olson: Given that the oldest primate fossils discovered so far date back only 55 million years, your estimate of how long primate species’ development has gone on is sheer speculation.

Speaker 1 Summary
Carrillo argues his statistical model shows that the first primates developed 81.5 million years ago.

Speaker 2 Summary
Olson believes that Carillo’s estimate is purely speculative because the oldest primate fossils found date back to 55 million years ago.

Objective
Disagreement: Carillo and Olsen disagree over whether Carillo’s model is accurate.

A
primates have been around for more than 55 million years
Carrillo agrees with this because he believes that the first primate developed around 81.5 million years ago. However, Olsen also agrees! He says that the oldest fossil dates back 55 million years, implying that the first primate was older than 55 million years old
B
Carrillo’s statistical model is a reliable way of dating the first appearance of primate species
Carrillo certainly agrees that his model is correct. Olson directly states that Carrillo's model is based on “pure speculation,” making it unreliable.
C
the available sample of primate fossils is representative of the variety of primate species that have existed
This answer choice is far too broad for either speaker to have a position on. Olson only discusses *one* fossil, while Carrillo is primarily focused on the results of his model. You have to make a lot of assumptions to make this work.
D
the dating of the primate fossils that Olson cites is accurate
Olson certainly agrees that his citation is correct. However, Carillo does not challenge or address this at all. Carillo’s discovery and Olson’s citation could both be correct. It is possible that the earliest primate fossil has never been discovered.
E
fossils of the first primate species that developed have been discovered
Carrillo does not address this statement at all, and it is implied that Olson disagrees. He acknowledges that the oldest fossils discovered “so far” date back 55 million years. He likely believes that there could be older fossils that have yet to be discovered.

10 comments