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

2A.defended

B.concluded

C.withdrawn

D.advised

3A.for

B.with

C.on

D.by

5A.tests

B.objects

C.examples

D.samples

4A.compared

B.sought

C.separated

D.connected

12A.drive

B.observe

C.confuse

D.limit

13A.according to

B.rather than

C.regardless of

D.along with

16A.forecast

B.remember

C.understand

D.express

17A.unpredictable

B.contributory

C.controllable

D.disruptive

18A.endeavor

B.decision

C.arrangement

D.tendency

7A.visit

B.miss

C.seek

D.know

8A.resemble

B.influence

C.favor

D.surpass

9A.again

B.also

C.instead

D.thus

10A.Meanwhile

B.Furthermore

C.Likewise

D.Perhaps

11A.about

B.to

C.from

D.like

14A.chances

B.responses

C.missions

D.benefits

15A.later

B.slower

C.faster

D.earlier

6A.insignificant

B.unexpected

C.incredible

D.unbelievable

19A.political

B.religious

C.ethnic

D.economic

20A.see

B.show

C.prove

D.tell

请帮忙给出每个问题的正确答案和分析，谢谢！