Identical twins tend to have similar personalities; if environment outweighs heredity in personality development, twins raised together should presumably have more similar personalities than those raised apart. A recent study of identical twins in both situations measured 11 key traits through a questionnaire, and concluded that 7 of the 11 are primarily products of heredity.
Which of the following, if established, would cast the most doubt on the study’s results?
(A) Fewer than half of the pairs of twins studied were raised separately.
(B) The ages of all of the twins studied fell within a 10-year range.
(C) Some of the traits that the study attributed to heredity developed in the separately raised twins because those pairs all grew up in similar families.
(D) Although over half the traits measured were determined to be linked to heredity, the nature of those traits varied widely.（C）
(E) The 11 traits that were measured constitute a representative sample of larger, generally accepted pool of key personality traits
这题没人问过，呵呵。
答案是c.。但是A为什么不是削弱？A说样本中很少的双胞胎是在一起长大的，那么大部分都是在一起长大的，固然又很多相似的特点，这些特点有可能是后天形成的，而不是遗传因素。正好削弱了结论。如果说大部分的样本是分开长大的，那么就加强了结论。迷惑，请牛人帮忙！！ | 
