Few scientific fields are as full of risk as that of research into human intelligence. The two questions that (1) over and over again are "is it a result of nature or nurture" and "does race make a difference"
Making (2) comments about the second question can be a (3) move, as James Watson, a co-discoverer of DNA structure, recently found. He suggested that he was " (4) about the prospect of Africa" (5) "all our social policies are based on the fact that their intelligence is the same as ours (white people) (6) all the testing says not really". Such (7) by Dr. Watson are not merely (8) , they are scientifically weird. If the term (9) has any useful scientific meaning, then Africa, the continent where modern humanity began, is most racially diverse. The resulting (10) among the public forced Dr. Watson to leave his laboratory.
(11) , the study of the first question (12) between intelligence and genetics— has some wiser practitioners. One of them, Terrie Moffitt, of King’s College, has just (13) a project judging the relative importance of nature and nurture. Dr. Moffitt’s team (14) the effect on intelligence of breastfeeding, but in a genetic context. Previous studies have shown that breastfed children are more intelligent, (15) about six IQ points, than those given baby formulas.
The team, however, (16) the involvement of a gene called FADS2, which comes in two varieties, known as C and G. The researchers (17) if these two varieties interacted differently with breast milk. (18) on data from two groups of people, they found that the intelligence increase associated with breastfeeding only happened to people having (19) at least one copy of the C variety. The effect did not. (20) on the social classes or IQs of the parents.
5（）
A.therefore
B.because
C.so
D.but
参考答案：B
解析：
[试题考点] 上下文逻辑关系与连词用法辨析。
[解题思路] 本题空格前的内容意为“他暗示对非洲的未来感到悲观”，空格后的句子意为“______所有的社会政策都是基于非洲人与向人智力相同的事实而制定的，______所有的实验结果表明情况并非如此”。由此可知，正是由于如今社会政策的制定以一个错误的结论(非洲人不和白人智力水平一致)为基础，而导致Dr. Watson对非洲未来感到悲观，故空格前后内容为因果关系，且文中结果在前，原因住后，四个选项中只有选项[B]because符合要求。
[干扰排除] 选项[A]therefore和选项[C]so都表示因果关系，但二者在使用时，所引出的是结果，而非原因，故可排除。选项[D]but表示转折，显然与文意不符，应排除。