The idea that some groups of people may be more intelligent than others is one of those hypotheses that dare not speak its name.But Gregory Cochran is 1 to say it anyway.He is that 2 bird,a scientist who works independently 3 any institution.He helped popularize the idea that some diseases not 4 thought to have a bacterial cause were actually infections,which aroused much controversy when it was first suggested.5 he,however,might tremble at the 6 of what he is about to do.Together with another two scientists,he is publishing a paper which not only 7 that one group of humanity is more intelligent than the others,but explains the process that has brought this about.The group in 8 are a particular people originated from central Europe.The process is natural selection.This group generally do well in IQ test,9 12-15 points above the 10 value of 100,and have contributed 11 to the intellectual and cultural life of the West,as the 12 of their elites,including several world-renowned scientists,13.They also suffer more often than most people from a number of nasty genetic diseases,such as breast cancer.These facts,14,have previously been thought unrelated.The former has been 15 to social effects,such as a strong tradition of 16 education.The latter was seen as a（an）17 of genetic isolation.Dr.Cochran suggests that the intelligence and diseases are intimately 18.His argument is that the unusual history of these people has 19 them to unique evolutionary pressures that have resulted in this 20 state of affairs.2选？
从文章内容看，显然该空填入的词应该是用来形容Cochran是一个什么样的人的。从上文我们可以看到，他总是做一些常人不敢做的事情，显然这个词既要表现他这类人很少，同时要表达出作者对Cochran正面评价，突出其优秀性，四个词中只有D能表达这种语义，故答案为D。本题从另一个角度来说，a rare bird是一固定搭配，指一类人。其他三个词与bird搭配都不能指人，同样得出答案为D。
