Samples From The Floor Of A Rock Shelter In Pennsylvania Were Dated GMAT Critical Reasoning

Question: Samples from the floor of a rock shelter in Pennsylvania were dated by analyzing the carbon they contained. The dates assigned to samples associated with human activities formed a consistent series, beginning with the present and going back in time, a series that was correlated with the depth from which the samples came. The oldest and deepest sample was dated at 19,650 years before the present, plus or minus 2,400 years. Skeptic, viewing that date as too early and inconsistent with the accepted date of human migration into North America, suggested that the samples could have been contaminated by dissolved old carbon carried by percolating groundwater from nearby coal deposits.

Which one of the following considerations, if true, argues most strongly against the suggestion of the skeptics?

1. No likely mechanism of contamination involving percolating groundwater would have affected the deeper samples from the site without affecting the uppermost sample.
2. Not every application of the carbon-dating procedure has led to results that have been generally acceptable to scientists.
3. There is no evidence that people were using coal for fuel at any time when the deepest layer might have been laid down.
4. No sample in the series, when retested by the carbon-dating procedure, was assigned an earlier date than that assigned to a sample from a layer above it.
5. No North American site besides the one in Pennsylvania has ever yielded a sample to which the carbon-dating procedure assigned a date that was comparably ancient.

“Samples from the floor of a rock shelter in Pennsylvania were dated ”- is a GMAT question about critical thinking. A candidate may choose to either find evidence that would undermine the argument or present an argument that is illogical in order to respond to the question. The GMAT critical reasoning gauges a candidate's aptitude for logic and analysis. Candidates must identify the argument's advantages and disadvantages as well as its logical flaws for this topic. Out of the 36 GMAT verbal questions, 10–13 critical reasoning questions are found.

Answer: A
Explanation:

By examining the carbon they contained, samples from the floor of a rock shelter in Pennsylvania were given a date. Dates assigned to samples connected to human activity were organized into a series that was correlated with the depth from which the samples were taken. This was started in the present and moved back in time. Plus or minus 2,400 years, the oldest and deepest sample was dated at 19,650 years before the present. The samples may have been contaminated by dissolved old carbon carried by percolating groundwater from nearby coal deposits. This was suggested by skeptics who considered that date to be too early and inconsistent with the accepted date of human migration into North America.

Let's examine each choice separately to find the right answer that fits the requirements in the question.

Option A : Correct

This option states that the deeper samples from the site would not have been unaffected by any likely mechanism of contamination involving percolating groundwater. It appears to support at first glance, but it doesn't. As a result, this option is the right choice.

Option B : Incorrect

This option states that not all uses of the carbon-dating method have produced outcomes that scientists can generally accept. Although this is true, it has no bearing on the passage. As a result, this option is ruled out.

Option C : Incorrect

According to this alternative, there is no proof that people ever used coal as fuel during any period when the deepest layer may have formed. This one only barely touches the essential subject, but it uses a method about which we have no concerns. This is a wrong choice because contamination is not addressed.

Option D : Incorrect

This option states that no sample in the series was given a date that was earlier than the date given to a sample from a layer above it. This is being said when it was retested using the carbon-dating procedure. This is a wrong choice as it is not the appropriate consideration that argues most strongly against the suggestions belonging to skeptics.

Option E : Incorrect

This option also states something that is invalid. Only the Pennsylvanian site in North America has ever produced a sample to which the carbon-dating technique assigned a date that was as old as possible.This is a wrong answer as it is not the appropriate consideration that argues most strongly against the suggestions belonging to skeptics.

From the explanations given above, it is clear that the first option is the correct answer.

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