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.
