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 that the similar genes seem to be evolving (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.

答案精析：副词辨析题。此空为比较级形式，根据空格所在句的句意，这项研究的一个显著发现是相似的基因似乎比其他基因进化得 。由四个选项可知，一种是在比较速度的快慢，另一种是比较时间上的早晚。再根据空格后的语义进行判断，后文接着说到人类进化在过去的3万年内加快了步伐（human evolution picked pace in the last 30,000 years），pick pace意为“提速”。故本空应填入faster，和后文相呼应。

错项排除：原文中出现了last 30,000 years表示时间，用于干扰可能会错选为表示时间早晚的比较级，但此处应注意细节和句子主旨，picked pace表示速度加快，并非是时间早晚的问题。故排除A、D两项。上下文应是相互呼应的关系，并不是对立关系，B项和后文内容意思相反，故排除B项。