"Surprising" Phenomenon
Scientists began citing a smaller group of sources once they had easier access to a larger group of sources.
Objective
The right answer will be a hypothesis that explains why scientists ended up using a narrower range of sources after getting access to a larger range of sources. This explanation must account for some motivation or proclivity, be that general across disciplines or specific to the scientific community, to use less sources even when more sources are available. Alternatively, the explanation could account for some issue in the digitalized sources.
A
A few of the most authoritative scientific journals were among the first to offer full online access to their articles.
Even if the most authoritative journals were among the first to offer online access, the others eventually ended up online, as well. We need to know why scientists chose not to use these sources.
B
Scientists who wrote a lot of articles were the most enthusiastic about accessing journal articles online.
We’re not concerned about a subset of scientists. The correct answer will discuss scientists in general.
C
Scientists are more likely to cite articles by scientists that they know than they are to cite articles by scientists they have never met, even if the latter are more prominent.
If scientists generally cite people they know, then they probably aren’t citing the same articles as their peers at different institutions. This seems to contradict the stimulus rather than resolve it.
D
Several new scientific journals appeared at roughly the same time that full online access to scientific articles became commonplace.
A couple new scientific journals doesn’t change much. We don’t even know when these journals went online.
E
Online searching made it easier for scientists to identify the articles that present the most highly regarded views on an issue, which they prefer to cite.
Scientists can simply search for eminent articles rather than sifting through journals as before. These articles are generally preferred, so many scientists end up citing them. Thus, there’s less variety in the articles scientists choose to cite.
Summarize Argument: Phenomenon-Hypothesis
The author concludes that we should not conclude that volcanic activity caused the short-term spike in sulfur dioxide on Venus. This is based on the fact that no active volcanoes have been identified on Venus, and planetary atmospheres are known to undergo cyclical variations in chemical composition.
Notable Assumptions
The author assumes that inactive volcanoes could not have produced a short-term spike in sulfur dioxide on Venus. The author also assumes that there aren’t any active volcanoes that we haven’t identified on Venus that could have produced the spike. Another assumption is that the cyclical variations in chemical composition could have accounted for the spike in sulfur dioxide.
A
Conditions on Venus make it unlikely that any instrument targeting Venus would detect a volcanic eruption directly.
This suggests that there might be active volcanoes on Venus that we haven’t identified. If we can’t identify eruptions directly, that raises the possibility that our failure to identify active volcanoes doesn’t guarantee the absence of active volcanoes on Venus.
B
Evidence suggests that there was a short-term spike in sulfur dioxide in Venus’s atmosphere 30 years earlier.
It’s not clear what a short-term spike 30 years ago has to do with the short-term spike detected recently.
C
Levels of sulfur dioxide have been higher in Venus’s atmosphere than in Earth’s atmosphere over the long term.
We detected a short-term spike in sulfur dioxide on Venus. Comparative levels of sulfur dioxide on Venus and Earth don’t shed light on the cause of a short-term spike.
D
Traces of the sulfur dioxide from volcanic eruptions on Earth are detectable in the atmosphere years after the eruptions take place.
This suggests that traces of sulfur dioxide can last a long time from volcanoes. But this doesn’t explain a short-term spike in sulfur dioxide. We’re not just trying to explain the presence of sulfur dioxide in the atmosphere; we’re trying to explain a short-term spike.
E
Most instances of sulfur dioxide spikes in the Earth’s atmosphere are caused by the burning of fossil fuels.
If anything, this might strengthen the author’s argument by suggesting another explanation for the short-term spikes on Venus besides volcanoes.
"Surprising" Phenomenon
Why do some land managers use a reforestation strategy that involves planting a single fast-growing tree species when their goal is to create an area with multiple tree species?
Objective
The right answer will be a hypothesis that either describes a benefit of the fast-growing-single-tree-species method or else a drawback of the seemingly obvious approach of planting multiple tree species.
A
Tree species that require abundant sunlight tend to grow quickly on degraded land.
This is irrelevant. Presumably, there are multiple tree species that require abundant sunlight to grow, so why wouldn’t land managers plant a variety of those species rather than just one fast-growing species?
B
An area with a multitude of thriving tree species tends to be more aesthetically pleasing than an area with only a single tree species.
This is irrelevant. We already know that the goal of reforestation is to create an area with a multitude of tree species, and we don’t need another reason why that’s a good thing to do. We just need to know how planting one fast-growing species helps achieve that goal.
C
The reforestation of degraded land is generally unsuccessful unless the land is planted with tree species that are native to the area designated for reforestation.
There are likely multiple tree species that are native to any given area, so why wouldn’t land managers just plant all those species rather than focusing on only one? We also don’t even know if the chosen fast-growing species are native to the degraded areas!
D
The growth of trees attracts wildlife whose activities contribute to the dispersal of a large variety of tree seeds from surrounding areas.
This explains why some land managers plant one fast-growing tree species! As those trees rapidly grow, wildlife come to the area, and with them they carry a large variety of tree seeds from nearby regions. Those seeds grow into trees and the goal of reforestation is complete!
E
The process of reforesting degraded sites is time consuming and labor intensive.
This is a blanket statement that doesn’t tell us anything that differentiates or explains distinct reforestation methods. Because we’re looking for an explanation of one specific reforestation method, this answer choice isn’t helpful.