Which of the following most logically completes the reasoning?Either food scarc

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问题 Which of the following most logically completes the reasoning?
Either food scarcity or excessive hunting can threaten a population of animals. If the group faces food scarcity, individuals in the group will reach reproductive maturity later than otherwise. If the group faces excessive hunting, individuals that reach reproductive maturity earlier will come to predominate. Therefore, it should be possible to determine whether prehistoric mastodons became extinct because of food scarcity or human hunting, since there are fossilized mastodon remains from both before and after mastodon populations declined, and__________.

选项 A、there are more fossilized mastodon remains from the period before mastodon populations began to decline than from after that period
B、the average age at which mastodons from a given period reached reproductive maturity can be established from their fossilized remains
C、it can be accurately estimated from fossilized remains when mastodons became extinct
D、it is not known when humans first began hunting mastodons
E、climate changes may have gradually reduced the food available to mastodons

答案 B

解析 Argument Construction
Situation In a population of animals, food scarcity causes later reproductive maturity; if that population is hunted excessively, earlier-maturing animals will be more numerous in the population.
Reasoning What point would most logically complete the argument? For the information given to be of use in determining what caused mastodons’extinction, mastodon fossils would need to indicate the are at which mastodons reached reproductive maturity, since that is what the argument suggests can indicate cause of extinction. If fossilized remains exist from before and after mastodon populations began to decline, and if the age at which those fossilized mastodons reached reproductive maturity can be determined, then we will have a good idea of what caused their extinction: if they reached reproductive maturity late, it was probably food scarcity, but if they matured earlier, it was most likely hunting.
A This fact only helps indicate that there was a decline; it tells us nothing about what caused the decline.
B Correct. This statement properly identifies a point that logically completes the argument: it explains how the fossilized mastodon remains could be used to help determine what caused mastodons’ extinction.
C The point at which mastodons became extinct is not part of this argument, which is concerned with the cause of their extinction. The only way in which this could be relevant to the issue at hand is if mastodons became extinct before humans took up hunting mastodons—but the argument includes no informatior on whether this was so.
D Not knowing when humans began hunting mastodons would have no effect on the argument, which is concerned with how mastodon fossils, combined with knowledge about how food scarcity and hunting affect mastodon reproductive maturity, can help determine how mastodons became extinct.
E This fact only shows that food scarcity may have led to mastodon’s decline. It tells us nothing about whether fossilized remains can help determine whether it was food scarcity or human hunting that actually led to the decline.
The correct answer is B.
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