Final answer:
The nurse's response is based on the information that the fontanels, also known as 'soft spots', on a baby's head gradually ossify and close after birth. The posterior fontanel typically closes after one year, while the anterior fontanel closes around one and a half years after birth.
Step-by-step explanation:
The nurse's response is based on the information that the fontanels, also known as 'soft spots', on a baby's head gradually ossify and close after birth. The two largest fontanels are the anterior (frontal) fontanel and the posterior (occipital) fontanel. The posterior fontanel typically closes after one year, while the anterior fontanel closes around one and a half years after birth.