It is reported that the sense of smell plays a dominant role in the social interactions of all land animals except humans.Then the question arises：Is this because humans don't use their noses in social settings the way all other land animals do？Or is this behavior covert （隱蔽的），rather than overt，in humans？
   In fact，this is exactly what Inbal Ravreby，a graduate student in Prof.Noam Sobel's laboratory in Weizmann's Brain Sciences Department，tried to answer.And as several lines of evidence suggest that humans are constantly，although mostly subconsciously，sniffing themselves and others，Ravreby supposed that the latter is the case.
   To test her hypothesis，Ravreby conducted the study with pairs of click friends：same-sex nonromantic friends whose friendships had originally formed very rapidly.Because such friendships emerge prior to an in-depth acquaintance，they may be particularly influenced by physiological characteristics such as body smell.She then collected body smell samples from these click friends and conducted two sets of experiments to compare the samples with those collected from random pairs of jye.aidividuals.In one set of experiments，she performed the comparison with a device known as an electronic nose，or eNose，which assessed the chemical signatures of the smells.In the other，she asked volunteers to smell the two groups of body smell samples in order to assess similarities measured by human perception.In both types of experiments，click friends were found to smell significantly more like each other than the individuals in the random pairs.
   Next，to rule out the possibility that body smell similarity was a consequence of click friendships，rather than a contributing cause，Ravreby performed an additional set of experiments，in which she used the eNose to "smell" a number of volunteers who were complete strangers to one another，and then asked them to engage in nonverbal （非言語的） social interactions in pairs.After each such structured interaction，the participants rated the other individual in terms of how much they liked that person.Subsequent analysis revealed that the individuals who had more positive interactions indeed smelled more like each other，as determined by the eNose.
   "These results imply that，as the saying goes，there is chemistry in social chemistry，" Ravreby concludes.However，Sobel offers words of caution， "This is not to say that we act like dogs or goats — humans likely rely on other，far more dominant signals in their social decision-making.Nevertheless，our study's results do suggest that our nose plays a bigger role than previously thought in our choice of friends."

（1）What did Inbal Ravreby want to figure out？

D

D

A．Whether humans have a sharp sense of smell.
B．Whether humans' noses can detect all types of smells.
C．Whether it is necessary for humans to sniff other people.
D．Whether the sense of smell plays a role in humans' interaction.
（2）What makes the first two sets of experiments different from each other？

A

A

A．The way to make comparisons.
B．The participation of random pairs.
C．The way volunteers used the eNose.
D．The number of pairs of click friends.
（3）Why did Ravreby involve complete strangers in the following experiments？

A

A

A．To determine the reliability of the finding.
B．To avoid interactions between click friends.
C．To make the experiments much more interesting.
D．To test the accuracy of the eNose in smell analysis.
（4）What is Sobel's attitude towards the research finding？

C

C

A．Disapproving.
B．Doubtful.
C．Positive.
D．Indifferent.