Human impacts on the natural environment during the later part of the Holocene (beginningabout 4,000 years ago) complicate investigations into environmental change during that period because the signals produced by human- and climate-inducedchange 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 changein vegetation could alternatively be attributed to human impact in the form of agricultural development. Examples of such human impactfrom 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?
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.
• 第一句：作者提出自己观点：人类影响因素使得对4000年前开始，环境变化的调查研究复杂化(complicate into)，因为人类和气候诱发的环境变化的signal经常难以区分开
• 第三句：然而，这种4000年前人类影响的例子是比较少的哦(small-scale),因为广泛采用农业技术导致的环境变化后来才大规模的发生(changes occurred later)
B选项，call into question，表示反驳，错!
When studying shrimp feeding from hydro-thermal vents at the bottom of the ocean, biologists were surprised that the shrimps’ reproductive cycles followed seasonal patterns. Far beyond the reach of sunlight, and with food abundant around the vents all year round, why should such animals reproduce seasonally? The answer might involve their offspring, which in their larval form drift in the currents to colonize new vents. The larvae must feed during their trip, and their spring time release coincides with a peak in algae raining down from surface waters. So far,
researchers have found no evidence of seasonal breeding among vent-dwelling species that provide their offspring with yolk to sustain them or among vent-dwelling species found in areas of the ocean with not seasonal algae blooms.
Which of the following best describes the function of the highlighted sentence?
A. It casts doubt on the accuracy of earlier observations of seasonal breeding among shrimp species living near hydro-thermal vents.
B. It undermines the explanation proposed for seasonal breeding among some shrimp species living near hydro-thermal vents.
C. It suggests that alternative theories are needed to explain seasonal breeding among shrimp species living near hydro-thermal vents.
D. It describes the survival benefits to shrimp of mating in parts of the ocean where algae blooms rain down abundantly.
E. It supports the explanation proffered for the seasonal breeding observed among some shrimp species living near hydro-thermal vents.