As many people hit middle age,they often start to notice that their memory and mental clarity are not what they used to be.We suddenly can’t remember___1___we put the keys just a moment ago,or an old acquaintance’s name,or the name of an old band we used to love.As the brain___2___,we refer to these occurrences as“senior moments.”___3___seemingly innocent,this loss of mental focus can potentially have a（n）___4___impact on our professional,social,and personal___5___.Neuroscientists,experts who study the nervous system,are increasingly showing that there’s actually a lot that can be done.It___6___out that the brain needs exercise in much the same way our muscles do,and the right mental___7___can significantly improve our basic cognitive___8___.Thinking is essentially a___9___of making connections in the brain.To a certain extent,our ability to___10___in making the connections that drive intelligence is inherited.___11___,because these connections are made through effort and practice,scientists believe that intelligence can expand and fluctuate___12___mental effort.Now,a new Web-based company has taken it a step___13___and developed the first“brain training program”designed to actually help people improve and regain their mental___14___.The Web-based program___15___you to systematically improve your memory and attention skills.The program keeps___16___of your progress and provides detailed feedback___17___your performance and improvement.Most importantly,it___18___modifies and enhances the games you play to___19___on the strengths you are developing—much like a（n）___20___exercise routine requires you to increase resistance and vary your muscle use.（11）选？
上下文逻辑关系+副词辨析本句句意为“_____，由于构建这些连接需要通过努力和实践才能实现，科学家们相信智力可……而提高和波动。”由此可知，本句意为“这种能力可以增强和变化”。而上一句提到“这种能力是遗传的”的，很显然前后两句构成了转折对比关系。因此选项A是正确答案。选项B引导递进关系，选项C经常引导的是可能的结果，而下文分析的不是假设性的结果，选项D引导因果关系，因此选项BCD均可排除。
