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  3. Human impacts on the natural environment during the later part of the Holocene (beginning about 4,000 years ago) complicate inve

Human impacts on the natural environment during the later part of the Holocene (beginning about 4,000 years ago) complicate inve

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问题 Human impacts on the natural environment during the later part of the Holocene (beginning about 4,000 years ago) complicate investigations into environmental change during the period because the signals produced by human- and climate-induced change are sometimes difficult to separate. For example, in the later Holocene, one indicator of increased aridity due to climate change is an increase in pollen from grasses, as forest gives way to grassland. Such a change in vegetation could alternatively be attributed to human impact in the form of agricultural development. Examples of such human impact from 4,000 years ago would be small-scale, however, since the broad ecosystem changes brought about by the widespread adoption of agricultural technologies occurred later.
Which of the following best describes the function of the highlighted sentence in the context of the passage as a whole?
选项 A、It provides an example of the kind of problems that often complicate investigations into environmental change.
B、It calls into question the reliability of the established dates for later Holocene agricultural development.
C、It describes the nature of localized agricultural developments during the later Holocene.
D、It outlines a hypothesis that draws on evidence discussed earlier in the passage.
E、It limits the scope of a particular complication mentioned earlier in the passage.
答案E
解析 a particular complication mentioned earlier in the passage指的是第一句的观点：人类活动使得人们去研究Holocene时期的环境变化变得很复杂。本题定位在第四句，反驳第一句，认为人类活动在Holocene时期规模很小，也就意味着这种研究的复杂程度并不大。E正确。
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