A research study reports that a particular educational program has improved the prospects

for success in later schooling for those children aged three to five who were subjects of the study. It follows, then, that introducing similar programs for all children aged three to five will improve their chances for success in later schooling. Which of the following, if true, would most weaken the argument above？

A．The parents of preschool children in the United States are attracted to educational fads and do not have a clear idea of what sorts of early education programs might benefit their children.

B．The cognitive abilities of children are constantly changing between ages three and five.

C．The researchers unwittingly included a substantial number of children who had been previously exposed to another educational enrichment program.

D．Many parents erroneously presume that early formal instruction takes up time that children could better spend exploring their worlds independently.

E．It would require extraordinary public expense to establish such educational enrichment programs on a national basis.