Are you a social butterfly, or do you prefer being at the edge of a group of friends? Either way, your genes and evolution may play a major  1  , US researchers reported on Monday.

While it may come as no surprise that genes may help explain  2  some people have many friends and others have  3  , the researchers said, their findings go just a little farther than that.

"Some of the things we find are  4    uncommon," said Nicholas Christakis of Harvard University in Massachusetts, who helped   5  the study.

"We find that how interconnected your friends are   6   on your genes. Some people have four friends who know each other and some people have four friends who don't  7  each other.  8     Dick and Harry know each other depends on Tom's  9    ," Christakis said in a telephone interview.

Christakis and colleague James Fowler of the University of California San Diego are  10     known for their studies that show obesity, smoking and happiness spread in networks.

For this study, they and Christopher Dawes of UCSD used national data that   11   more than 1,000 identical(同卵的) and fraternal（异卵的） twins’ genes. Because  12  share an environment, these studies are good for showing the impact that genes have  13  various things, because identical twins  14  all their genes while fraternal twins share just half.

"We found there appears to be a genetic tendency to introduce your friends  15  each other," Christakis said.

There could be good, evolutionary reasons  16  this. People in the middle of a social network could be secret to useful gossip,  17   the location of food or good investment choices.

But they would also be at risk of catching effects from all sides -- in which case the advantage would  18   more cautious social behavior, they wrote in the Proceedings of the National Academy of Sciences.

"It may be that natural selection is  19  not just things like whether or not we can resist the common cold, but also who it is that we are going to come into  20   with," Fowler said in a statement.

(    ) 1. A. role                 B. rule           C. roll                  D. pole

(    ) 2. A. where              B. why          C. when                D. how

(    ) 3. A. a few                      B. several      C. few                  D. some

(    ) 4. A. generally          B. mainly      C. mostly              D. frankly

(    ) 5. A. conduct            B. introduce   C. conflict            D. instruct

(    ) 6. A. depends            B. bases         C. take                 D. put

(    ) 7. A. see                   B. inspect      C. learn                D. know

(    ) 8. A. When               B. Where       C. What                D. Whether

(    ) 9. A. genes                      B. brains        C. appearances      D. figures

(    ) 10. A. much             B. best           C. very                 D. least

(    ) 11. A. recorded         B. illustrated C. described          D. compared

(    ) 12. A. brothers          B. sisters        C. twins                D. cousins

(    ) 13. A. with                      B. on             C. for                   D. to

(    ) 14. A. share              B. have          C. own                 D. show

(    ) 15. A. into                B. to             C. in                    D. from

(    ) 16. A. for                 B. with          C. to                    D. at

(    ) 17. A. in addition to B. due to       C. as for                      D. such as

(    ) 18. A. lie on             B. bring in     C. lie in                D. send in

(    ) 19. A. acting on               B. putting on C. relying on         D. sending on

(    ) 20. A. contract          B. face          C. join                  D. contact

Are you a social butterfly, or do you prefer being at the edge of a group of friends? Either way, your genes and evolution may play a major  1  , US researchers reported on Monday.

While it may come as no surprise that genes may help explain  2  some people have many friends and others have  3  , the researchers said, their findings go just a little farther than that.

"Some of the things we find are  4    uncommon," said Nicholas Christakis of Harvard University in Massachusetts, who helped   5  the study.

"We find that how interconnected your friends are   6   on your genes. Some people have four friends who know each other and some people have four friends who don't  7  each other.  8     Dick and Harry know each other depends on Tom's  9    ," Christakis said in a telephone interview.

Christakis and colleague James Fowler of the University of California San Diego are  10     known for their studies that show obesity, smoking and happiness spread in networks.

For this study, they and Christopher Dawes of UCSD used national data that   11   more than 1,000 identical(同卵的) and fraternal（异卵的） twins’ genes. Because  12  share an environment, these studies are good for showing the impact that genes have  13  various things, because identical twins  14  all their genes while fraternal twins share just half.

"We found there appears to be a genetic tendency to introduce your friends  15  each other," Christakis said.

There could be good, evolutionary reasons  16  this. People in the middle of a social network could be secret to useful gossip,  17   the location of food or good investment choices.

But they would also be at risk of catching effects from all sides -- in which case the advantage would  18   more cautious social behavior, they wrote in the Proceedings of the National Academy of Sciences.

"It may be that natural selection is  19  not just things like whether or not we can resist the common cold, but also who it is that we are going to come into  20   with," Fowler said in a statement.

(    ) 1. A. role                 B. rule           C. roll                  D. pole

(    ) 2. A. where                  B. why          C. when               D. how

(    ) 3. A. a few                      B. several      C. few                  D. some

(    ) 4. A. generally          B. mainly      C. mostly              D. frankly

(    ) 5. A. conduct            B. introduce   C. conflict            D. instruct

(    ) 6. A. depends            B. bases        C. take                 D. put

(    ) 7. A. see                   B. inspect      C. learn               D. know

(    ) 8. A. When                   B. Where       C. What               D. Whether

(    ) 9. A. genes                      B. brains        C. appearances      D. figures

(    ) 10. A. much             B. best           C. very                 D. least

(    ) 11. A. recorded        B. illustrated C. described          D. compared

(    ) 12. A. brothers          B. sisters        C. twins               D. cousins

(    ) 13. A. with                      B. on             C. for                   D. to

(    ) 14. A. share              B. have          C. own                 D. show

(    ) 15. A. into               B. to             C. in                    D. from

(    ) 16. A. for                 B. with          C. to                    D. at

(    ) 17. A. in addition to B. due to       C. as for                      D. such as

(    ) 18. A. lie on             B. bring in     C. lie in               D. send in

(    ) 19. A. acting on               B. putting on C. relying on        D. sending on

(    ) 20. A. contract          B. face          C. join                  D. contact

Are you a social butterfly, or do you prefer being at the edge of a group of friends? Either way, your genes and evolution may play a major1, US researchers reported on Monday.
While it may come as no surprise that genes may help explain 2some people have many friends and others have 3 , the researchers said, their findings go just a little farther than that.
"Some of the things we find are4uncommon," said Nicholas Christakis of Harvard University in Massachusetts, who helped5the study.
"We find that how interconnected your friends are6on your genes. Some people have four friends who know each other and some people have four friends who don't7each other. 8Dick and Harry know each other depends on Tom's 9 ," Christakis said in a telephone interview.
Christakis and colleague James Fowler of the University of California San Diego are 10known for their studies that show obesity, smoking and happiness spread in networks.
For this study, they and Christopher Dawes of UCSD used national data that11more than 1,000 identical(同卵的) and fraternal(异卵的) twins’ genes. Because 12share an environment, these studies are good for showing the impact that genes have13various things, because identical twins14all their genes while fraternal twins share just half.
"We found there appears to be a genetic tendency to introduce your friends15each other," Christakis said.
There could be good, evolutionary reasons16this. People in the middle of a social network could be secret to useful gossip,17the location of food or good investment choices.
But they would also be at risk of catching effects from all sides -- in which case the advantage would18more cautious social behavior, they wrote in the Proceedings of the National Academy of Sciences.
"It may be that natural selection is19not just things like whether or not we can resist the common cold, but also who it is that we are going to come into 20with," Fowler said in a statement.

1. 1.
   1. A.
      role
   2. B.
      rule
   3. C.
      roll
   4. D.
      pole
2. 2.
   1. A.
      where
   2. B.
      why
   3. C.
      when
   4. D.
      how
3. 3.
   1. A.
      a few
   2. B.
      several
   3. C.
      few
   4. D.
      some
4. 4.
   1. A.
      generally
   2. B.
      mainly
   3. C.
      mostly
   4. D.
      frankly
5. 5.
   1. A.
      conduct
   2. B.
      introduce
   3. C.
      conflict
   4. D.
      instruct
6. 6.
   1. A.
      depends
   2. B.
      bases
   3. C.
      take
   4. D.
      put
7. 7.
   1. A.
      see
   2. B.
      inspect
   3. C.
      learn
   4. D.
      know
8. 8.
   1. A.
      When
   2. B.
      Where
   3. C.
      What
   4. D.
      Whether
9. 9.
   1. A.
      genes
   2. B.
      brains
   3. C.
      appearances
   4. D.
      figures
10. 10.
    1. A.
       much
    2. B.
       best
    3. C.
       very
    4. D.
       least
11. 11.
    1. A.
       recorded
    2. B.
       illustrated
    3. C.
       described
    4. D.
       compared
12. 12.
    1. A.
       brothers
    2. B.
       sisters
    3. C.
       twins
    4. D.
       cousins
13. 13.
    1. A.
       with
    2. B.
       on
    3. C.
       for
    4. D.
       to
14. 14.
    1. A.
       share
    2. B.
       have
    3. C.
       own
    4. D.
       show
15. 15.
    1. A.
       into
    2. B.
       to
    3. C.
       in
    4. D.
       from
16. 16.
    1. A.
       for
    2. B.
       with
    3. C.
       to
    4. D.
       at
17. 17.
    1. A.
       in addition to
    2. B.
       due to
    3. C.
       as for
    4. D.
       such as
18. 18.
    1. A.
       lie on
    2. B.
       bring in
    3. C.
       lie in
    4. D.
       send in
19. 19.
    1. A.
       acting on
    2. B.
       putting on
    3. C.
       relying on
    4. D.
       sending on
20. 20.
    1. A.
       contract
    2. B.
       face
    3. C.
       join
    4. D.
       contact