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.