19. 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.

正确答案是Ｃ．为什么Ａ不对啊？请教ＮＮ？

我这题也错了，但是后来发觉是自己理解太差：A recent study of identical twins in both situations measured 11 key traits through a questionnaire，这句话里的both situations表示有两批双胞胎，一批一起养大，还有一批分开养大，但是最后结果发现他们共同的特质与遗传有关。

所以反对的答案就是：那批分开养大的双胞胎其实在差不多的家庭里生长（即环境类似）

而A好像针对了条件，属于无关选项。

终于明白了.谢谢!

看来，我也是没有明白选项的意思.