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  3. While chemists try to assemble molecules using a combination of theoretical principles and practical experience to mold m

While chemists try to assemble molecules using a combination of theoretical principles and practical experience to mold m

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问题            While chemists try to assemble molecules using a combination of theoretical
       principles and practical experience to mold molecules that have desired
       structural and chemical properties, nanotechonologists generally seek to make
Line    more than a single molecule. They build arrays of identical or complexed
(5)      molecules, sometimes on a scale that will transcend the boundaries of the
       microscopic and approach the macroscopic, using both top-down and bottom-up
       approaches. The first is exemplified by scientists who build objects and
       molecular arrays using the techniques of scanning probe microscopy, while the
       second is exemplified by investigators who design two-and three-dimensional
(10)     chemical systems that cohere according to the rules of chemical interactions.
       The top-down approach has exquisite precision, but its disadvantage is its lack
       of extensive parallelism; it requires manipulating atoms and molecules
       practically one by one, while the bottom-up approach is massively parallel. But
       in both cases, scientists are forced to use the difficult nanometer scale, i.e. the
(15)     level at which living systems tend to make their structural components, rather
       than the angstrom scale of chemistry.
The primary purpose of the passage is to
选项 A、indicate some possible technological benefits to the development of new and varied techniques in nanotechnology
B、argue that science involving the macroscopic tends to be exponentially more difficult than the science of the microscopic
C、defend the use of the bottom-up approach of building molecules as more efficient relative to the top-down approach
D、distinguish two different approaches in nanotechnology and comment on their differences and similarities
E、correct the misconception that the benefits of nanotechnology are likely to be seen in the near future
答案D
解析
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