Final answer:
The nurse should inform the parents that their 10-month-old child understands object permanence--the concept that objects still exist even when they're not visible. This developmental milestone is typical for infants around 8 months of age.
Step-by-step explanation:
The nurse should instruct the parents that c. the child understands the permanence of objects even though the child cannot see them. This concept, known as object permanence, is a cognitive developmental milestone that infants typically grasp by around 8 months old. By 10 months, infants recognize that objects continue to exist even when out of view, which is an important cognitive skill that precedes more advanced problem-solving and memory retention abilities.
Between 5 and 8 months of age, children develop object permanence, indicating they understand that something can still exist even when it cannot be seen, as evidenced by their actions of looking for objects that have been hidden or removed from their view. By 10 months, this understanding is evident in behavior such as searching for a dropped toy. These milestones are based on the foundational research on cognitive development by Jean Piaget, who highlighted the progression of children's understanding of objects and their permanence as they grow.