Summary
Almost all mail that is correctly addressed gets to its destination within 2 business days of being sent.
If correctly addressed mail takes longer than 2 business days to reach its destination, it must be damaged in transit.
Most mail arrives more than 2 business days after being sent.
If correctly addressed mail takes longer than 2 business days to reach its destination, it must be damaged in transit.
Most mail arrives more than 2 business days after being sent.
Notable Valid Inferences
If almost all mail that’s correctly addressed gets to its destination within 2 business days, but most mail arrives more than 2 business days after being sent, that means a significant portion of overall mail must be incorrectly addressed. If this were not the case, then we’d expect most mail to arrive within 2 business days. But most mail takes longer to arrive.
A
A large proportion of the mail that is correctly addressed is damaged in transit.
Could be false. It’s possible only a tiny proportion of correctly addressed mail is damaged in transit. After all, nearly all correctly addressed mail arrives within 2 business days, so those pieces don’t have to be damaged.
B
No incorrectly addressed mail arrives within two business days of being sent.
Could be false. Some incorrectly addressed mail could arrive within two days. We were never told incorrectly addressed mail always takes longer than two days.
C
Most mail that arrives within two business days of being sent is correctly addressed.
Could be false. Most mail that arrives within 2 days might be incorrectly addressed. For example, there are 5 correct pieces and 20 incorrect pieces. 4 correct pieces and 5 incorrect pieces could arrive within 2 days. In this example most of the 2-day arrivals are incorrect.
D
A large proportion of mail is incorrectly addressed.
Must be true. If this weren’t true, we’d expect most mail to arrive within 2 days, because nearly all correctly addressed mail arrives within 2 days. So there has to be a large proportion of incorrectly addressed mail in order for most mail overall to take longer than 2 days.
E
More mail arrives within two business days of being sent than arrives between two and three business days after being sent.
Could be false. We know most mail takes longer than 2 days to arrive. It’s possible, for example, that all of this later-than-2-day mail arrives between 2 and 3 days after being sent. So more mail can arrive between 2 and 3 days of being sent than within 2 days.
Summarize Argument
The author concludes that insufficient consumption of fiber causes colon cancer, and sufficient consumption of fiber prevents it. This is based on the fact that numerous studies show a negative correlation between high-fiber diets and colon cancer.
Identify and Describe Flaw
The author assumes that the reason there’s a negative correlation between high-fiber diets and colon cancer is that high-fiber prevents colon cancer. This overlooks alternate explanations for the correlation. For example, there might be something else that is associated with high-fiber diets that helps prevent colon cancer. Or perhaps having colon cancer causes one to reduce one’s fiber intake.
A
the consumption of fiber in many countries is rising appreciably
This possibility doesn’t undermine the argument, because we have no idea whether colon cancer rates are increasing or decreasing in these countries.
B
the risk of many types of cancer is reduced by high-fiber diets
If anything, this might strengthen the argument by establishing a stronger connection between high-fiber diets and cancer reduction.
C
fiber is difficult for many people to include in their diets
The difficulty of including fiber in a diet has no bearing on whether the negative correlation between high-fiber and colon cancer is due to high-fiber preventing colon cancer.
D
the fiber in fruits and vegetables and the fiber in cereals have cancer-fighting properties to different degrees
The author never assumed that fiber in fruits/veggies and fiber in cereals had the exact same level of cancer-fighting properties. There can be differences; this doesn’t undermine the author’s reasoning.
E
foods containing fiber also contain other substances that, when consumed, tend to prevent colon cancer
This possibility, if true, shows that the negative correlation between high-fiber and colon cancer might be explained by the other substances in foods that contain fiber. It could be these other substances that reduce colon cancer, and not the fiber.
Summarize Argument: Counter-Position
Chimpanzees do not necessarily have human-like language because, contrary to popular belief, humans did not evolve directly from chimpanzees. Instead, both species evolved from a common ancestor. As a result, the development of language in humans could have occurred after the extinction of this common ancestor, which means chimpanzees would not have developed the same language as humans.
Identify Conclusion
Chimpanzees may not have a human-like language.
A
Humans did not evolve from chimpanzees, but rather from some extinct species.
This statement is a premise that counters the misconception that humans evolved from chimpanzees. It supports the author’s argument that because humans and chimpanzees did not evolve directly from one another, chimpanzees do not necessarily have human-like language.
B
The assumption that something like human language must exist in some species from which humans evolved has no clearcut linguistic implications for chimpanzees.
This correctly states the conclusion: people assume that species from which humans evolved have human-like language, but this assumption doesn’t apply to chimpanzees since humans didn’t evolve from them. Thus, this assumption doesn’t tell us anything about chimpanzees’ language.
C
The communicative systems of chimpanzees are cruder than human language.
The stimulus does not make this claim. The anthropologist argues that chimpanzees do not necessarily have human-like language but doesn’t describe their language or compare it to human language. Since this claim is not made, it cannot be the main conclusion.
D
Human language is a by-product of human intelligence, which chimpanzees lack.
The stimulus doesn’t make this claim. The anthropologist argues that chimpanzees don’t necessarily have human-like language because humans didn’t evolve from chimpanzees, not because chimpanzees lack human intelligence. As this claim isn’t made, it can’t be the main conclusion.
E
The evolution of human language began after the disappearance of an extinct species from which both humans and chimpanzees evolved.
The stimulus does not make this claim. The anthropologist suggests that human language might have developed after the extinction of a common ancestor but does not assert this as a certainty. Additionally, this idea is part of the argument’s premise, not its main conclusion.