请教feifei-119的B选项为什么不对？

119. For a television program about astrology, investigators went into the street and found twenty volunteers born under the sign of Gemini who were willing to be interviewed on the program and to take a personality test. The test confirmed the investigators’ personal impressions that each of the volunteers was more sociable and extroverted than people are on average. This modest investigation thus supports the claim that one’s astrological birth sign influences one’s personality.

Which one of the following, if true, indicates the most serious flaw in the method used by the investigators?

A.        The personality test was not administered or scored personally by the investigators.

B.        People born under astrological signs other than Gemini have been judged by astrologers to be much less sociable than those born under Gemini.

C.        The personal impressions the investigators first formed of other people have tended to be confirmed by the investigators’ late experience of those people.

D.       There is not likely to be a greater proportion of people born under the sign of Gemini on the street than in the population as a whole.

E.        People who are not sociable and extroverted are not likely to agree to participate in such an investigation.

我看到原题的时候就想到，本实验只用Gemini的样本就得到有关全体样本的结论，样本并不具有代表性。所以一看到B就选B了，都没有向下看其他选项。现在还是觉得B也对啊，因为其他城市的双子座的人远远比G城市的双子做的人的样本less sociable。因此说明了样本的不一致，所以原方法有错误！为什么B不对呢？