Final answer:
The nurse should reassure the mother that the infant's behavior is normal for a 6-month-old.
Step-by-step explanation:
The best response by the nurse would be option 2: "This behavior is normal for a 6-month-old infant." Around six months of age, infants typically develop the ability to transfer objects from one hand to another. It is a normal milestone in their motor skills development. The nurse can reassure the mother that her baby's behavior is within the expected range of development.