Pediatrician: Child psychologists recommend that mothers of one-year-olds not only name objects in the immediate environment, but that they include the color of the object, when applicable. For instance, if a mother hands her child a red ball, she should say, "This is a red ball." Nonetheless, even if mothers began to name the color, instead of simply saying, "This is a ball," no real benefit will be conferred to the child, because studies have shown that children under 18-months old do not grasp the notion of color.

The pediatrician's argument is most vulnerable to which of the following?

A:Infants who hear words embedded in sentences that have each part of speech present tend to speak sooner than those infants who do not.

B:Children usually benefit from having toys in their environments.

C:The range at which children utter their first sentence typically ranges from 15-months to 30-months.

D:Children under the age of three tend to be confused when parents use adult level vocabulary.

E:Psychologists have conducted studies showing that most children under the age of 30 months often utter the names of colors even when that color is not present in their environments.