Thousands of years ago, in North America's past, all of its megafauna—large mammals such as mammoths andgiantbears—disappeared. Oneproposedexplanation for this event is that when the first Americans migrated over from Asia, they hunted the megafauna toextinction. These people, known as the Clovis society after a site where theirdistinctivespearpoints were first found, would have been able to use this foodsourcetoexpandtheirpopulationand fill thecontinentrapidly. Yet many scientistsargueagainst this "Pleistoceneoverkill"hypothesis. Modern humans have certainly beencapableof suchdrasticeffects on animals, but couldancientpeople with little more than stone spears similarly have caused theextinctionofnumerousspeciesof animals? Thirty-five genera or groups ofspecies(and manyindividualspecies) sufferedextinctionin North America around 11,000 B.C., soon after theappearanceandexpansionof Paleo-lndiansthroughoutthe Americas (27 genera disappeared completely, and another 8 becamelocallyextinct, surviving only outside North America).

Although theclimatechanged at the end of thePleistocene, warming trends had happened before. A period ofmassiveextinctionof large mammals like that seen about 11,000 years ago had not occurred during theprevious400,000 years, despite these changes. The only apparentlysignificantdifferencein the Americas 11,000 years ago was the presence of human hunters of these large mammals. Was this coincidence or cause-and-effect?

We do not know. Ecologist Paul S. Martin has championed the model that associates theextinctionof large mammals at the end of thePleistocenewith humanpredation. With researcher J. E. Mosimann, he has co-authored a work in which a computer model showed that in around 300 years, given the right conditions, a smallinfluxof hunters into eastern Beringia 12,000 years ago could havespreadacross North America in a wave and wiped out game animals to feed theirburgeoningpopulation.

The researchers ran the model several ways, always beginning with apopulationof 100 humans in Edmonton, in Alberta, Canada, at 11,500 years ago. Assuming differentinitialNorth American big-game-animal populations (75-150 million animals) and differentpopulationgrowth rates for the human settlers (0.65%-3.5%), and varying kill rates, Mosimann and Martin derived figures of between 279 and 1,157 years frominitialcontactto big-gameextinction.

Many scholars continue to support thisscenario. For example,geologistLarry Agenbroad has mapped the locations ofdatedClovis sites alongside thedistributionofdatedsites where the remains of wooly mammoths have been found in botharchaeologicaland purely paleontological contexts. These distributions showremarkablesynchronicity (occurrenceat the same time).

There are, however, many problems with this model. Significantly, though a few sites are quiteimpressive, there really is very littlearchaeologicalevidenceto support it. Writing in 1982, Martin himself admitted thepaucityofevidence; for example, at that point, the remains of only 38individualmammoths had been found at Clovis sites. In the years since, fewadditionalmammoths have been added to the list; there are still fewer than 20 Clovis sites where the remains of one or more mammoths have been recovered, aminusculeproportionof the millions that necessarily would have had to have been slaughteredwithintheoverkillscenario.

Though Martin claims thelackofevidenceactually supports his model—theevidenceissparsebecause thespreadof humans and theextinctionof animals occurred so quickly—thisargumentseems weak. And how could we ever disprove it? As archaeologist Donald Grayson points out, in other cases whereextinctionresulted from the quickspreadof human hunters—for example, theextinctionof themoa, the largeflightlessbird of New Zealand—archaeologicalevidencein the form of remains isabundant. Grayson has also shown that theevidenceis not so clear that all or even most of the large herbivores in latePleistoceneAmerica becameextinctafter theappearanceof Clovis. Of the 35extinctgenera, only 8 can be confidently assigned anextinctiondate of between 12,000 and 10,000 years ago. Many of the older genera, Grayson argues, may have succumbed before 12,000 B.C., atleasthalf acenturybefore the Clovis showed up in the American West.

Questions:
question_stem: The word "proposed" in the passage is closest in meaning to
choices: tag: A
text: accepted

tag: B
text: obvious

tag: C
text: debatable

tag: D
text: suggested
answer_key: D
explanation: 【题目翻译】 "proposed" 这个词的意思与下列哪个词的意思最接近？
A 选项：accepted 意思是“被接受” 
B 选项：obvious 意思是“明显的”
C 选项：debatable 意思是“有争议的” 
D 选项：suggested 的意思是“被提议的”

【判断题型】题目要求选出与高亮单词意思最接近的选项，故判断本题为词汇题。

【关键词定位】词汇所在句子“One proposed explanation for this event is that when the first Americans migrated over from Asia, they hunted the megafauna to extinction.”

【词汇解析】“proposed”的意思是“被提议，建议”，文章所在的句子的意思是“对此事件的被提出一个解释是，当第一批美国人从亚洲迁移过来时，他们狩猎巨型动物以至于使其灭绝。” 

【选项分析】
A 选项：accepted 意思是“被接受”，排除。 
B 选项：obvious 意思是“明显的”，排除。 
C 选项：debatable 意思是“有争议的”，排除。 
D 选项：suggested 的意思是“被提议的”，意思最为贴近，故为正确答案。

question_stem: The word "distinctive" in the passage is closest in meaning to
choices: tag: A
text: hidden

tag: B
text: characteristic

tag: C
text: scattered

tag: D
text: rare
answer_key: B
explanation: 【题目翻译】在文章中单词“distinctive”与下列哪个单词意思最为接近？
A 选项：hidden 意思是“隐藏的”
B 选项：characteristic 意思是“特有的，典型的”
C 选项：scattered 意思是“分散的”
D 选项：rare 的意思是“稀有的”

【判断题型】题目要求选出与高亮单词意思最接近的选项，故判断本题为词汇题。

【关键词定位】词汇所在句子“These people, known as the Clovis society after a site where their distinctive spear points were first found, would have been able to use this food source to expand their population and fill the continent rapidly.”

【词汇解析】“distinctive”的意思是“有特色的，与众不同的 ”，词汇所在句子“These people, known as the Clovis society after a site where their distinctive spear points were first found, would have been able to use this food source to expand their population and fill the continent rapidly.”的意思是“大家熟知的克洛维斯社会，那是第一个被发现有独特矛尖的地方，这些人们能够使用这些食物源来扩展他们的人口，并且很快的充满了整个大陆。” 

【选项分析】
A 选项：hidden 意思是“隐藏的”，排除。
B 选项：characteristic 意思是“特有的，典型的”，意思最为贴近，故为正确答案。 
C 选项：scattered 意思是“分散的”，排除。 
D 选项：rare 的意思是“稀有的”，排除。

question_stem: Why does the author compare "Modern humans" with "ancient people"?
choices: tag: A
text: To argue that modern people have continued to have drastic effects on animal species

tag: B
text: To illustrate how people from different historical times treated animals differently

tag: C
text: To question the idea that ancient people could have hunted the megafauna to extinction

tag: D
text: To emphasize that modern people are more successful hunters than ancient people were
answer_key: C
explanation: 【题目翻译】为什么作者要将现代人和古代人相比较？
A：认为现代人对动物物种的影响仍然很大。
B：说明不同历史时期的人对待动物的方式不同。
C：质疑古人可能已经猎杀这种大型动物灭绝的想法。
D：强调现代人比古代人更擅长狩猎。

【判断题型】根据题干问法“why …… ”，题目询问“compare "Modern humans" with "ancient people"的修辞目的，可以判断本题为修辞目的题。

【关键词定位】由题干可以定位到句子“Modern humans have certainly been capable of such drastic effects on animals, but could ancient people with little more than stone spears similarly have caused the extinction of numerous species of animals?”

【引用内容分析】题干所定位的句子的意思是“现代人对动物确实具有如此强烈的影响力，但几乎只有石矛的古代人同样也能造成无数种动物的灭绝吗？”其实是作者提出的一个疑问。

【选项分析】
A 选项说为了说明现代人一直以来都对动物种类有着大量影响，错误，这篇文章的主要对象是古代人，重点错误。 
B 选项说揭示人们在不同历史时期如何不同地对待动物，与原句所想表达的意思不符。 C 选项说来表达对古代人是否可以狩猎大型动物导致灭绝的疑问，符合原句意义，故为正确答案。 
D 选项说为了强调现代人比古代人是更成功的猎手，错误，曲解原意。

question_stem: In using the word "coincidence" in the passage, the author refers to events that occurred
choices: tag: A
text: after a period of many years

tag: B
text: subsequent to a prediction

tag: C
text: from time to time

tag: D
text: at the same time and by chance
answer_key: D
explanation: 【题目翻译】在文章中使用“巧合”这个词时，作者指的是事件发生在___？
A 在许多年之后
B 继预言之后
C 时不时的
D 在相同时间并且偶然发生 

【判断题型】根据题干中出现的关键词“refer”等其他表示暗指推断的词，判定本题为推理题。

【关键词定位】定位到原文“The only apparently significant difference in the Americas 11,000 years ago was the presence of human hunters of these large mammals. Was this coincidence or cause-and-effect?”

【逻辑分析】文章中的句子的意思是“唯一明显重大的差别是在11000年前的美洲这些大型哺乳动物猎人存在了。这是巧合还是因果关系呢？”文章还提到了地质学家 Larry Agenbroad 已经在地图上标识出了那个时期的克洛维斯遗址的位置以及在考古学和生物学立场下发现羊毛猛犸一体的遗址分布。这些分布显示出明显的同步性（同时发生）。

【选项分析】
A 选项说这个事件是发生在许多年之后，不符合 coincidence 的意思。 
B 选项说这件事是继预言之后，也不符合原意。 
C 选项说这件事的发生是时不时的，意思错误。 
D 选项说这件事是同时且偶然发生的，与巧合的意思相同，故为正确答案。

question_stem: According to paragraph 2, what suggests that human activity played a role in the extinction of mammals about 11,000 years ago?
choices: tag: A
text: Climate changes that would have favored human population expansion occurred at the time of the extinctions.

tag: B
text: The presence of human hunters had caused animal extinctions in other time periods.

tag: C
text: There was a pattern of climate change earlier than 11,000 years ago that had not caused animal extinctions.

tag: D
text: Harmful climate changes 11,000 years ago would have required humans to hunt larger numbers of animals for food.
answer_key: C
explanation: 【题目翻译】根据第2段，大约110000年前，人类活动在哺乳动物的灭绝中起到了什么作用？
A 在物种灭绝之时，发生了有利于人口膨胀的气候变化。
B 人类狩猎者的出现导致了其他时期的动物灭绝。
C 早在11000年前，就有一种气候变化模式尚未导致动物灭绝。
D 在11000年前，有害的气候变化要求人类捕猎更多的动物作为食物。

【判断题型】题目问的是文章中的具体细节信息，故根据题目问法可以判断本题为事实信息题。

【关键词定位】定位到句子“Although the climate changed at the end of the Pleistocene, warming trends had happened before. A period of massive extinction of large mammals like that seen about 11,000 years ago had not occurred during the previous 400,000 years, despite these changes.”

【逻辑分析】
根据题目所问，是什么暗示了人类活动才是导致动物灭绝的原因。意思是“尽管更新世末期气候发生了变化，但变暖趋势发生在此之前。 尽管发生了这些变化，但在过去的40万年中，大约11，000年前，大型哺乳动物大规模灭绝的时期并没有出现。” 

【选项分析】
A 选项说气候变化为适合人类人口增长导致了当时的灭绝，文章并没有提及气候变化得适合人口增长，无法推断。 
B 选项说人类猎手的存在，在其他时期导致了动物灭绝，错误，文章就没有提及其他时期。 
C 选项说在早于11000年前，气候变化的模式并没有导致动物灭绝，因而表示动物灭绝另有原因，而之后又说了灭绝是出现在人类猎手出现之时的，能推断出人类活动才是导致动物灭绝。 
D 选项说有危害的气候变化在11000年前将使得人们去狩猎更大数量的动物作为食物，错误，无法从原文推断出气候促使人们去捕食大数量动物。

question_stem: Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information
choices: tag: A
text: A computer model was designed to determine how long it would have taken for a small group of hunters to spread across North America.

tag: B
text: A computer model showed that it was possible for a small group of hunters to spread across North America and kill off game animals in just 300 years.

tag: C
text: According to a computer model, people coming into North America 12,000 years ago had to kill game animals in order to feed their population.

tag: D
text: According to a computer model, about 12,000 years ago conditions enabled a small group of hunters to enter and cross North America in about 300 years.
answer_key: B
explanation: 【题目翻译】下面哪个句子最能表达文章中突出句子的基本信息？不正确的选择会以重要方式改变含义，或者遗漏重要信息。
A：一个计算机模型被设计用来确定一小群猎人要花多长时间才能横跨北美洲。
B：计算机模型显示，一小群猎人有可能在短短300年内遍布北美洲并杀死猎物。
C：根据一个计算机模型，12000年前来到北美洲的人们为了养活他们的人口，不得不杀死野生动物。
D：根据计算机模型，大约12000年前的条件使得一小群猎人能够在大约300年内进入和穿越北美。

【判断题型】根据题目问法，题目要求选择和高亮句意思逻辑都最为接近的句子，故判断本题为句子简化题。

【句子分析】原句为: With researcher J. E. Mosimann, he has co-authored a work in which a computer model showed that in around 300 years, given the right conditions, a small influx of hunters into eastern Beringia 12.000 years ago could have spread across North America in a wave and wiped out game animals to feed their burgeoning population. 意思是“研究人员 JE Mosimann 与他合作撰写了一个计算机模型的研究报告，在大约300年的时间里，考虑到正确的条件，12,000年前在 Beringia 东部的小量涌入的猎人就能够以波浪的形式传播到北美洲， 消灭野兽以养活其新生人口。” 

【选项分析】
A 选项说计算机模型的设计是为了确定一小群猎人需要多长时间才能在北美蔓延。原文的重点在于12,000年前 Beringia 东部的传播到北美，而不在于多长时间，侧重点错误，排除。 
B 选项说一个计算机模型显示，一小群猎人可能在北美蔓延，并在短短300年内杀死野兽。重要信息俱全，逻辑正确，wiped out 是 kill off 的同义替换，故为正确答案。 
C 选项说根据计算机模型，12000年前来到北美洲的人必须杀死猎物以喂养他们的人口。选项逻辑和原文不符，且缺少300年这个关键信息。 
D 选项说根据计算机模型，大约12，000年前的条件使得一小群猎人在大约300年内进入并穿越北美。错误，缺少关于猎杀动物的关键信息。

question_stem: Which of the following best describes the results of the research discussed in paragraph 4?
choices: tag: A
text: Scientists used mathematical models to show that most of the extinctions occurred in areas where humans had recently arrived.

tag: B
text: Scientists established that the main population of North Americans who hunted lived in Canada during the time of the megafauna extinctions.

tag: C
text: Scientists used numerical models to confirm that a small population of humans could have caused big-game extinctions in a relatively short period of time.

tag: D
text: Scientists used statistics to prove beyond doubt the currently accepted view that human hunters were the main cause of the megafauna extinctions.
answer_key: C
explanation: 【题目翻译】下列哪一项最能描述第4段所讨论的研究结果？
A：科学家用数学模型表明，大多数物种灭绝发生在人类最近到达的地区。
B：科学家们证实，在大型动物灭绝期间，北美洲的主要狩猎者居住在加拿大。
C：科学家用数值模型来证实一小部分人可能在相对较短的时间内导致大型动物灭绝。
D：科学家利用统计数字毫无疑问地证明了目前公认的观点，即人类狩猎者是大型动物灭绝的主要原因。

【判断题型】题目问的是文章中的具体细节信息，故根据题目问法可以判断本题为事实信息题。

【关键词定位】找到第四段中：Assuming different initial North American big-game-animal populations (75-150 million animals) and different population growth rates for the human settlers (0.65%-3.5%), and varying kill rates, Mosimann and Martin derived figures of between 279 and 1,157 years from initial contact to big-game extinction.

【逻辑分析】得出的数据结果是人类从最初开始接触到大型生物到其灭绝的这段时间是在279年到1157年之间。即一小部分人可能在相对较短的时间内导致大型动物灭绝。

【选项分析】
A：科学家们使用数学模型来表明大多数的灭绝发生在人类最近到达的地区，错误，原文没有提到是人类“最近到达”，所以排除。 
B：科学家们确定，在巨型动物灭绝期间，狩猎的大部分北美人居住在加拿大，错误，原文只是说研究者拿加拿大的100人作为数据分析，并非推断历史事实。 
C：科学家们使用数值模型来证实一小群人可能会在相对较短的时间内造成大猎物灭绝，选项中的“big-game”还有大猎物的意思，而这句话是最贴近选段的意义的，故为正确答案。 
D：科学家利用统计数据来证明人类捕猎者是巨型动物灭绝的主要原因，这是毫无疑问的，理解错误，文中提到了关键的时间因素此处并没有说到，而这个模型也并不是用来证明人类是导致巨型动物灭绝的主要原因，故排除。

question_stem: Which of the following statements about Larry Agenbroad's work is implied in the discussion in paragraph 5?
choices: tag: A
text: Agenbroad showed that Mosimann and Martin's estimates of the amount of time needed to drive big-game to extinction were correct.

tag: B
text: Agenbroad's maps were the first to indicate the ages of the Clovis sites.

tag: C
text: Agenbroad reinforced the idea that humans could have caused the extinctions.

tag: D
text: Agenbroad's studies of wooly mammoths led to his discovery of Clovis sites.
answer_key: C
explanation: 【题目翻译】关于拉里·阿根布洛德的工作，以下哪个陈述在第5段的讨论中被暗示？
A 阿根布罗德表明，莫斯曼和马丁对驱使大型猎物灭绝所需时间的估计是正确的。
B 阿根布罗德的地图是首次标明克洛维斯遗址的年代。
C Agenwide 强调了人类可能导致物种灭绝的观点。
D 阿根布罗德对长毛猛犸象的研究使他发现了克洛维斯遗址。

【判断题型】根据题干中出现的关键词“imply"，判定本题为推理题。

【关键词定位】由 Larry Agenbroad’s work 可以找到 geologist Larry Agenbroad has mapped the locations of dated Clovis sites alongside the distribution of dated sites where the remains of wooly mammoths have been found in both archaeological and purely paleontological contexts. These distributions show remarkable synchronicity (occurrence at the same time). 

【逻辑分析】文章中定位的句子翻译为：地质学家 Larry Agenbroad 已经绘制了那个时期的克洛维斯遗址的位置，以及考古遗址的分布，在这些地方已经发现了羊毛猛犸遗体，这些都可以在考古学和纯粹生物学的文章中体现出来了。这些分布显示出明显的同步性（同时发生）。段落第一句所提到的“许多学者继续支持这种说法”此处指代的的应是前几段提到的生态学家保罗•马丁（Paul S. Martin）提出将更新世末期大型哺乳动物灭绝与人类捕食相关联的模式。

【选项分析】
A 选项为：Agenbroad 表明，莫西曼和马丁对驱使大型动物消亡所需时间的估计是正确的。错误，这里并非应和莫西曼和马丁的估算结果。 
B 选项为：Agenbroad 的地图首次显示了 Clovis 遗址的年代。原文并未提到是首次显示。 
C 选项：Agenbroad 强化了人类可能导致其灭绝的想法，正确，通过发现人文遗迹中的大型动物化石来说明人类可能是导致其灭绝的原因。 
D 选项：Agenbroad 对猛犸兽的研究导致了克洛维斯遗址的发现，错误，前后颠倒了，是绘制了遗址再发现的猛犸遗体。

question_stem: The word "admitted" in the passage is closest in meaning to
choices: tag: A
text: accepted the truth of

tag: B
text: was unaware of

tag: C
text: was troubled by

tag: D
text: called attention to
answer_key: A
explanation: 【题目翻译】在文章中单词“admitted”与下列哪个短语意思最为相近？
A 选项 accepted the truth of 的意思是“接受……的事实”
B 选项 was unaware of 的意思是“不知道”
C 选项 was troubled by 的意思是“被困扰”
D 选项 called attention to 的意思是“引起关注”

【判断题型】题目要求选出与高亮单词意思最接近的选项，故判断本题为词汇题。

【关键词定位】词汇所在句子“Martin himself admitted the paucity of evidence”

【词汇解析】“admitted”是被允许的意思，所在句子翻译为：马丁自己承认缺乏证据。

【选项分析】 
A 选项 accepted the truth of 的意思是“接受……的事实”，与原义接近，故为答案。 
B 选项 was unaware of 的意思是“不知道”，排除 
C 选项 was troubled by 的意思是“被困扰”,排除。 
D 选项 called attention to 的意思是“引起关注”,排除。

question_stem: According to paragraph 6, which of the following statements challenges the view that hunting by humans caused the extinctions of North American megafauna?
choices: tag: A
text: The Clovis sites that contain the remains of mammoths were settled by humans long after the extinctions occurred.

tag: B
text: Only a few of the Clovis sites are located near known mammoth habitats.

tag: C
text: No archaeological evidence of extinctions has been found at Clovis sites since 1982.

tag: D
text: The number of mammoth remains found at Clovis sites is smaller than would be expected if hunting by humans had caused the extinctions.
answer_key: D
explanation: 【题目翻译】根据第6段，下列哪项陈述挑战了人类狩猎导致北美大型动物灭绝的观点？
A：包含猛犸象遗骸的克洛维斯遗址在灭绝发生后很久就由人类定居下来。
B：只有少数的克洛维斯遗址位于已知的猛犸栖息地附近。
C：自1982年以来，在克洛维斯遗址没有发现灭绝的考古学证据。
D：在克洛维斯遗址发现的猛犸象遗骸数量比人类狩猎导致物种灭绝的预期要少。

【判断题型】题目问的是文章中的具体细节信息，故根据题目问法可以判断本题为事实信息题。

【关键词定位】定位原文“at that point, the remains of only 38 individual mammoths had been found at Clovis sites. In the years since, few additional mammoths have been added to the list; there are still fewer than 20 Clovis sites where the remains of one or more mammoths have been recovered, a minuscule proportion of the millions that necessarily would have had to have been slaughtered within the overkill scenario.

【逻辑分析】题目要求找出反驳人类狩猎导致大型动物灭绝的观点。定位句翻译为“例如，在那个时候，在克洛维斯遗址发现的只有38只个体猛犸象的遗骸，但是仍然有不到20个克洛维斯遗址，其中一头或多头猛犸象的遗体已经被恢复，数百万中的一些小部分必然会在过度屠杀的情况下被杀害。” 文章的最后一段列举了好几种动物的例子，来表明许多动物的灭绝并不是因为人类的狩猎。

【选项分析】
A：包含猛犸象遗骸的克洛维斯遗址在灭绝发生之后过了很久才被人类定居，未提及，可以排除。 
B: 只有少数克洛维斯遗址位于已知的猛犸栖息地附近，未提及，可以排除。 
C: 自1982年以来，克洛维斯地区没有发现有灭绝的考古证据，与原文矛盾，事实上有发现零星的证据，但不足以证明，所以排除。 
D：在克洛维斯遗址发现的庞然大物的数量比人类狩猎造成的灭绝所预期的要少，符合原文，为正确答案。

question_stem: In paragraph7, why does the author mention that there is abundant archaeological evidence for the extinction of the New Zealand moa?
choices: tag: A
text: To show that extinctions occurred in areas other than North America.

tag: B
text: To challenge Martin's claim that the lack of megafauna remains supports his model of the megafauna extinctions.

tag: C
text: To identify a country where humans were highly skilled as hunters.

tag: D
text: To help explain why it is unclear whether all large herbivores of late Pleistocene America became extinct after the appearance of Clovis.
answer_key: B
explanation: 【题目翻译】在第7段中，作者为什么要提到，有丰富的考古证据证明新西兰沼泽已经灭绝？
A：表明北美以外的地区发生了灭绝。
B：为了挑战马丁关于大型动物仍然缺乏的说法，他提出了大型动物灭绝的模型。
C：确定一个人类作为猎人具有高度技能的国家。
D：为了解释为什么还不清楚晚更新世美洲所有的大型草食动物在克洛维斯出现后是否都灭绝了。

【判断题型】根据题干问法“why …… mention”，可以判断本题为修辞目的题。

【定位关键词】定位第七段“Martin claims the lack of evidence actually supports his model”。

【逻辑分析】关键句的意思是：马丁声称缺乏证据实际上支持他的模型。而后面的这些证据都是来 disprove 这个观点的，题目问为何作者提了这些考古学证据。 

【选项分析】
A 选项：来表现在美国北部以外的地区发生了灭绝。 
B 选项：反驳了马丁所声称的巨型动物遗骸的缺失支持了他巨型动物灭绝模式的说法。 
C 选项：来识别一个人类非常擅长打猎的国家 
D 选项：为了解释为什么不清楚晚更新世美国的大型草食动物在 Clovis 出现后灭绝了。 上述选项从除了 B 点出了是反驳马丁观点，别的都未提及，所以都是错的。

question_stem: Paragraph 7 suggests that Donald Grayson believes which of the following about the remains at Clovis sites and megafaunal extinctions?
choices: tag: A
text: The rapid rate of the spread of humans explains why the extinctions also occurred at a rapid rate.

tag: B
text: The lack of evidence of human-caused extinctions is not surprising in view of the speed with which the extinctions occurred.

tag: C
text: It is likely that more evidence will be found as dating methods improve.

tag: D
text: If humans did contribute to the extinctions, much more evidence of that would have been found by now.
answer_key: D
explanation: 题目问第7段表明 Donald Grayson 相信以下哪一个关于 Clovis 遗址的遗骸和巨型动物灭绝？定位到“As archaeologist Donald Grayson points out, in other cases where extinction resulted from the quick spread of human hunters—for example, the extinction of the moa, the large flightless bird of New Zealand—archaeological evidence in the form of remains is abundant. Grayson has also shown that the evidence is not so clear that all or even most of the large herbivores in late Pleistocene America became extinct after the appearance of Clovis.”前面说其他的证据都由考古形式遗骸得到证明，而对于遗址和巨型动物灭绝的证据却很模糊。
A 选项：人类的快速传播解释了为什么灭绝也以很快的速度发生。原文并未提及两者关系。
B 选项：鉴于灭绝发生的速度，缺乏人类导致灭绝的迹象并不令人意外。原文没有关于 Donald 对此做出“并不令人意外”的表示。
C 选项：随着测定方法的改进，可能会发现更多证据。原文并没有关于对测定方法的论述，错误。
D 选项：人类如果确实对它们造成了灭绝，现在已经发现了更多的证据。这句话就是定位的句子的隐藏意义，故选 D。