Passage 42
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 that 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 vegetation 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.
1. Which of the following best describes the function of the highlighted sentence in the context of the passage as a whole?
A. It provides an example of the kind of problems that often complicate investigations into environmental change.
B. It call 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.
2. According to the passage, which of the following is true regarding environmental changes 4,000 years ago?
A. No localized increases in grass pollen were caused by agricultural development.
B. Increases in grass pollen were at least sometimes a reflection of an increase in aridity.
C. Wholesale ecosystem changes probably resulted from agricultural development.
D. Any small-scale changes occurring then would not be detectable now.
E. Environmental change helped induce the adoption of agricultural technologies.
答案：E B
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