Summarize Argument
The author concludes that no one should take the advice of so-called expert stock consultants. This is because 2,000 of the stocks such experts recommended on a TV show over the last 12 years performed worse than the market did over the same period.
Notable Assumptions
The author assumes that these 2,000 stocks are reflective of what the consultants recommend in general, without considering other stocks that may have also been recommended and performed well. The author also assumes that performance over this certain 12-year period is sufficient to draw conclusions about the consultants’ abilities to predict which stocks will do well. Perhaps the period in question was anomalous for some reason, or perhaps the stocks won’t pay off until a later date.
A
Taken together, the stocks recommended on the television show performed better than the market as a whole for the past year.
Evidently, it’s sometimes a good idea to take the consultants’ advice. Last year, their stocks outperformed the market.
B
Taken together, the stocks recommended on the television show performed better for the past 12-year period than stock portfolios that were actually selected by any other means.
Since you can’t buy the market itself, you have to put together a portfolio. Those portfolios all performed even worse than those selected by the consultants, meaning their advice was worthwhile.
C
Performance of the stocks recommended on the television show was measured by stock dividends, whereas the performance of the market as a whole was measured by change in share value.
The way the stocks and the market were measured differed. This means a comparative conclusion can’t be drawn about them.
D
Performance of the stocks recommended on the television show was measured independently by a number of analysts, and the results of all the measurements concurred.
Several different measurements confirmed the stocks recommended on the TV show performed worse than the market. This certainly doesn’t weaken the claim that the so-called expert consultants aren’t giving good advice.
E
The stock portfolios for which the guests were consultants performed better for the past 12-year period than the market as a whole.
Even if the recommended stocks didn’t all do well together, the consultants were nevertheless able to create decent portfolios using different combinations of stocks. This suggests their advice may be worthwhile.
Summary
Scientists examined diamonds formed 2.9 billion years ago and concluded these diamonds had higher-than-normal concentrations of sulfur-33. The only way this concentration occurs is from a chemical reaction triggered by ultraviolet light. If there was more than a trace of oxygen in the atmosphere 2.9 billion years ago, then not enough ultraviolet light would be present to cause the chemical reaction.
Strongly Supported Conclusions
2.9 billion years ago the atmosphere had at most very little oxygen.
A
Most diamonds with higher-than-normal concentrations of sulfur-33 were formed at least 2.9 billion years ago.
This answer is unsupported. We don’t know if this is true of most diamonds with this concentration. We only know from the stimulus that there are at least a few of them formed 2.9 billion years ago.
B
Ultraviolet light causes the oxygen in Earth’s atmosphere to react chemically with sulfur-33.
This answer is unsupported. We don’t know whether the oxygen is specifically reacting with sulfur-33. We only know from the stimulus that a “certain chemical reaction” occurs when stimulated by ultraviolet light.
C
Earth’s atmosphere contained very little, if any, oxygen 2.9 billion years ago.
This answer is strongly supported. This answer explains why the diamonds in the stimulus have higher than normal concentrations of sulfur-33.
D
Sulfur-33 is rarely found in diamonds that were formed more recently than 2.9 billion years ago.
This answer is unsupported. We don’t know anything about more recently formed diamonds from the stimulus. The stimulus is strictly limited to the diamonds scientists are examining from 2.9 billion years ago.
E
The formation of diamonds occurs only in the presence of ultraviolet light.
This answer is unsupported. We don’t know from the stimulus under what conditions diamonds are formed generally.
Summarize Argument: Phenomenon-Hypothesis
The author concludes dolphins have advanced cognitive abilities, possibly including language and foresight. Why? Because two particular dolphins sometimes show different, synchronized reactions to the same hand signal by their trainer.
Notable Assumptions
The author assumes there’s no explanation for the dolphins’ behavior besides their having complex brain functions. In particular, he assumes the dolphins’ movements are original and not planned by a human in any way. To conclude dolphins can use language, the author must assume they communicate before performing their synchronized actions.
A
Mammals have some resemblance to one another with respect to bodily function and brain structure.
This is irrelevant, whether it refers to individuals or whole species. Similarity between animals does not itself account for their ability to perform synchronized actions, nor does it suggest they have complex thought processes.
B
The dolphins often exhibit complex new responses to the hand signal.
This strengthens the argument because the originality of the dolphins’ movements supports the author’s subconclusion: they aren’t just rehearsing responses to a stimulus.
C
The dolphins are given food incentives as part of their training.
This is irrelevant. It doesn’t say the dolphins are coaxed with food to perform the particular actions described, nor that a potential food reward makes their cognitive responses necessarily complex.
D
Dolphins do not interact with humans the way they interact with one another.
This doesn’t mean dolphins communicate using language or display complex thought processes. They may interact differently simply because they’re reacting to different stimuli.
E
Some of the behaviors mentioned are exhibited by dolphins in their natural habitat.
This isn’t relevant without knowing which behaviors are exhibited naturally. It doesn’t say the dolphins naturally perform synchronized reactions or respond to the same stimulus in various ways.