Derek Is Playing with a Ball When It Rolls Under

Multiple Choice

Derek is playing with a ball when it rolls under the couch.Even though he cannot see where the ball went,Derek immediately starts to search for it.According to Piaget,what accounts for Derek's behaviour in response to this event?

A) He has not yet mastered object permanence.
B) He has not yet mastered conservation.
C) He has mastered the concept of conservation.
D) He has mastered the concept of object permanence.