单选题 Being an only child has little to do with a child's social development. A recent study that followed thirty only children and thirty-five first-born children to the age of three found that the two groups of children behaved very similarly to each other toward their peers, their parents, and other adults.
Which of the following, if true, most weakens the conclusion drawn above?

A、 The groups being compared did not contain the same number of children.
B、 More time was spent observing the interactions of children with their mothers than with their fathers.
C、 Most of the researchers involved in the study were persons who had no brothers or sisters.
D、 The first-born children were, on the average, nearly three when their parents had the second children.
E、 (E) The "other adults" described in the study consisted mainly of members of the research team.

【正确答案】 D

【答案解析】[解析] 本题根据3岁以前的独生子与第一胎的孩子的对比得出了是否是独生子与其社会能力发展无关的结论。要对该结论进行削弱，就要削弱支持该结论的那一组对比，凡是认为这组对比不具代表性或不具可比性的选项都能削弱本题的结论。(D)指出一般情况下，第一胎的孩子在接近3岁时，他们的父母才要第二个孩子，就充分说明了得出本题结论的那个调查中的两个对照组的特征基本一致，没有可对比性，因此(D)对本题的结论构成了反对，所以(D)正确。(A)不是主要问题；(B)引入了新的比较，必然不对。(C)和(E)都不能从本题的段落中推出，且都是无关选项。