How Did Piaget Determine Whether a Child Understands Object Permanence?​

Multiple Choice

How did Piaget determine whether a child understands object permanence?​

A) He asked the child to describe objects from memory.
B) ​He poured liquid from one container to another and asked which had "more."
C) ​He watched the child's eye movements when he moved a toy.
D) ​He watched whether the child would reach for a toy behind a barrier.