Though not biologically related， friends are as “related” as fourth cousins， sharing about 1% of genes. That is _（1）_a study， published from the University of California and Yale University in the Proceedings of the National Academy of Sciences， has__（2）__. The study is a genome-wide analysis conducted __（3）__1， 932 unique subjects which __（4）__pairs of unrelated friends and unrelated strangers. The same people were used in both_（5）__. While 1% may seem_（6）_， it is not so to a geneticist. As James Fowler， professor of medical genetics at UC San Diego， says， “Most people do not even _（7）_their fourth cousins but somehow manage to select as friends the people who_（8）_our kin.”The study_（9）_found that the genes for smell were something shared in friends but not genes for immunity .Why this similarity exists in smell genes is difficult to explain， for now， _（10）_， as the team suggests， it draws us to similar environments but there is more_（11）_it. There could be many mechanisms working together that _（12）_us in choosing genetically similar friends_（13）_“functional Kinship” of being friends with_（14）_！

One of the remarkable findings of the study was the similar genes seem to be evolution_（15）_than other genes Studying this could help_（16）_why human evolution picked pace in the last 30， 000 years， with social environment being a major_（17）_factor. The findings do not simply explain people's_（18）_to befriend those of similar_（19）_backgrounds， say the researchers. Though all the subjects were drawn from a population of European extraction， care was taken to_（20）_that all subjects， friends and strangers， were taken from the same population.

1. [A] when [B] why [C] how [D] what

2. [A] defended [B] concluded [C] withdrawn [D] advised

3. [A] for [B] with [C] on [D] by

4. [A] compared [B] sought [C] separated [D] connected

5. [A] tests [B] objects [C]samples [D] examples

6. [A] insignificant [B] unexpected [C]unbelievable [D] incredible

7. [A] visit [B] miss [C] seek [D] know

8. [A] resemble [B] influence [C] favor [D] surpass

9. [A] again [B] also [C] instead [D] thus

10. [A] Meanwhile [B] Furthermore [C] Likewise [D] Perhaps

11. [A] about [B] to [C]from [D]like

12. [A] drive [B] observe [C] confuse [D]limit

13. [A] according to [B] rather than [C] regardless of [D] along with

14. [A] chances [B]responses [C]missions [D]benefits

15. [A] later [B]slower [C] faster [D] earlier

16. [A]forecast [B]remember [C]understand [D]express

17. [A] unpredictable [B]contributory [C] controllable [D] disruptive

18. [A] endeavor [B]decision [C]arrangement [D] tendency

19. [A] political [B] religious [C] ethnic [D] economic

20. [A] see [B] show [C] prove [D] tell

【参考答案】DBCAC　ADABD　BABDC　CBDCA

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