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.
20（）
A.depend
B.focus
C.lean
D.count
参考答案：A
解析：
[试题考点] 上下文语意关系和动词词义辨析。
[解题思路] 本题空格处需填入一个动词，与介词on搭配。本句意为“这种影响不______父母的社会阶层或者IQ”，其中，“这种影响”指代上文中一直讨论的母乳喂养对人智力的影响。由于前一句提到“母乳喂养引起的智力提升只发生在那些遗传了至少一个C类基因副本的人身上”，简言之就是，母乳要影响智力，必须要有某种基因，故父母的社会阶层或者IQ是不起作用的。纵观各个选项，其中depend可与on搭配，构成“取决于；由……决定”的意思，符合文意，故为正确选项。
[干扰排除] 选项[B]focus与on搭配，意为“注意力集中于……；聚焦于……”。选项[C]lean与on构成搭配，意为“依靠；威胁”。选项[D]count与on搭配，意为“(在精神或者物质上)依靠”，其后一般跟人。将这三个选项带入空格，都不能形成通顺的文意，故可排除这三项。