Summarize Argument: Phenomenon-Hypothesis
The author hypothesizes that the eight large craters in a long straight line were probably caused by volcanic events rather than meteorites. This is because the craters contain rocks that show characteristics that could have been caused by volcanic events, and the linearity of the craters make it unlikely that the craters had different causes. In addition, the craters are all of different ages.
Notable Assumptions
The author assumes that craters in a straight line that are all of different ages are unlikely to be caused by meteorites slamming into earth. The author assumes that it is possible for volcanic events to produce craters in a straight line that are all of different ages. Another assumption is that there isn’t another more likely cause of the craters besides volcanic activity and meteorites.
A
A similar but shorter line of craters that are all the same age is known to have been caused by volcanic activity.
The craters we’re trying to explain are all of different ages. Evidence that volcanic activity can produce craters of the same age has no impact.
B
No known natural cause would likely account for eight meteorite craters of different ages forming a straight line.
In theory, meteorites could have hit Earth over a long time and left craters, but something covered up or removed some craters such that what’s left appears to be a straight line of craters. (B) strengthens the argument by eliminating this possibility.
C
There is no independent evidence of either meteorites or volcanic activity in the region where the craters are located.
If anything, this might weaken by suggesting the cause of the craters might be something besides volcanic activity.
D
There is no independent evidence of a volcanic event strong enough to have created the high-pressure shocks that are characteristic of meteorites slamming into Earth.
If anything, this might weaken by suggesting the cause of the craters might be something besides volcanic activity.
E
No known single meteor shower has created exactly eight impact craters that form a straight line.
The craters were all different ages, which already strongly suggests that the craters were not caused by a single meteor shower. So, (E) has no impact. The possibility we really want to eliminate is that they were created by multiple meteor showers over time.
Summary
Modern car washes use mitters rather than brushers. Mitters are easier on most cars’ finishes than brushes are. This is important today, because many cars have clear-coat finishes that are more easily scratched than older finishes.
Strongly Supported Conclusions
If brushes were used on cars today instead of mitters, more cars would have scratched finishes today than is currently the case.
A
When car washes all used brushes rather than mitters, there were more cars on the road with scratched finishes than there are today.
Unsupported. This doesn’t account for potential increases in population and car use. In the past, although there may have been a higher rate of scratches on cars, there may have been fewer cars overall. So, the overall number of scratched cars might have been lower in the past.
B
Modern “brushless” car washes were introduced as a direct response to the use of clear-coat finishes on cars.
Unsupported. We’re not told the reason modern car washes were introduced. The fact modern car washes are better for clear-coat finishes does not imply the clear-coat finishes caused modern washes to come about.
C
Modern “brushless” car washes usually do not produce visible scratches on cars with older finishes.
Strongly supported. Mitters are easier on most cars’ finishes than brushes. This is important because clear-coat finishes are more easily scratched. This suggests that when used on older finishes, mitters aren’t likely to produce scratches, at least not any we can see.
D
Brushes are more effective than mitters and are preferred for cleaning cars with older finishes.
Unsupported. We’re not told whether brushes or mitters are more effective for cleaning. We’re only told which one is easier on cars’ finishes.
E
More cars in use today have clear-coat finishes rather than older finishes.
Unsupported. We know that many cars today have clear-coat finishes. But we don’t know whether most (over half) cars today have such finishes.
The key to this question is understanding what an "effective hourly wage" means.
If you get paid a flat rate of $100, what's your "effective hourly wage"? Well, that depends on how many hours you worked. If you worked 1 hour, then you're "in effect" getting paid $100/hour. If you worked 10 hours, then you're "in effect" getting paid $10/hour.
Once you understand this, (B) should be obvious as the correct answer choice.
Summary
Taxi drivers’ income is based on their fares.
They often decide to finish work when they reach a daily income target.
They tend to work fewer hours on busy days than on slow days.
They often decide to finish work when they reach a daily income target.
They tend to work fewer hours on busy days than on slow days.
Notable Valid Inferences
Taxi drivers get more money per hour on busy days than on slow days.
A
The number of hours per day that a person is willing to work depends on that person’s financial needs.
This could be true. The stimulus does not give any indication on what considerations go into the drivers’ income targets. It could be the case that one’s financial needs determines their income target.
B
People work longer when their effective hourly wage is high than when it is low.
The stimulus provides clear evidence against this. The stimulus says that drivers stop working when they meet their income target; they will reach their income target more quickly when their hourly wage is high, so they will work fewer hours on these days.
C
Workers will accept a lower hourly wage in exchange for the freedom to set their own schedules.
This could be true; the stimulus does not give any information to indicate what wages they will accept in exchange for freedom over their schedules.
D
People are willing to work many hours a day in order to avoid a reduction in their standard of living.
This could be true; the stimulus does not contradict this. We don’t know how many hours “many” hours means, and we don’t know whether or not taxi drivers are hitting this threshold of “many hours.”
E
People who are paid based on their production work more efficiently than those who are paid a fixed hourly wage.
This could be true; the stimulus does not give any information that compares how efficiently people work under different payment systems.
Further Explanation
The key to this question is understanding what an "effective hourly wage" means.
If you get paid a total of $100 over the course of a day, what's your "effective hourly wage"? Well, that depends on how many hours you worked. If you worked 1 hour to make that $100, then you're "in effect" getting paid $100/hour. If you worked 10 hours to make that same $100, then you're "in effect" getting paid $10/hour ($100 divided by 10 hours).
Understanding this helps to make (B) clearer as the correct answer choice.