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? ['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.', 'Infants who hear words embedded in sentences that have each part of speech present tend to speak sooner than those infants who do not.', 'Children usually benefit from having toys in their environments.', 'The range at which children utter their first sentence typically ranges from 15-months to 30-months.']