My Space and other Web sites have unleashed a potent new phenomenon of social networking in cyberspace, (1) at the same time, a growing body of evidence is suggesting that traditional social (2) play a surprisingly powerful and under-recognized role in influencing how people behave.
The latest research comes from Dr. Nicholas A. Christakis, at the Harvard Medical School, and Dr. James H. Fowler, at the University of California at San Diego. The (3) reported last summer that obesity appeared to (4) from one person to another (5) social networks, almost like a virus or a fad. In a follow-up to that provocative research, the team has produced (6) findings about another major health (7) : smoking. In a study published last week in the New England Journal of Medicine, the team found that a person’s decision to (8) the habit is ply affected by (9) other people in their social network quit—even people they do not know. And, surprisingly, entire networks of smokers appear to quit virtually (10)
For (11) of their studies, they (12) of detailed records kept between 1971 and 2003 about 5,124 people who participated in the landmark Framingham Heart Study. Because many of the subjects had ties to the Boston suburb of Framingham, Mass. , many of the participants were (13) somehow—through spouses, neighbors, friends, co-workers—enabling the researchers to study a network that (14) 12,067 people.
Taken together, these studies are (15) a growing recognition that many behaviors are (16) by social networks in (17) that have not been fully understood. And (18) may be possible, the researchers say, to harness the power of these networks for many (19) , such as encouraging safe sex, getting more people to exercise or even (20) crime.
9（）
A.how
B.that
C.what
D.whether
参考答案：D
解析：
[考点] 逻辑关系
本题要求考生判断空格前后两个分句的逻辑关系，填入恰当的从句引导词。空格前有介词by，表明后面的从句为宾语从句，四个选项均可引导宾语从句。本句意思是“人们戒烟的决定被……影响”，即人们的戒烟行为受到交际圈他人行为的影响。决定有两个“戒”或“不戒”，取决于交往圈的状况，即交往圈里的其他人戒烟还是不戒烟，因此这个宾语从句应含有选择关系，因此D选项whether正确。
[干扰项分析] A选项how表示方式，“他人戒烟方式影响自己戒烟的决定”不符合主旨；B选项that所引导的宾语从句为单一事实的陈述；C选项what代表从句中所缺的名词性成分，空格后不缺成分，故C项应排除。