According to Piaget, a Child Who Has the Concept of Conservation

According to Piaget, a child who has the concept of conservation understands that

A) the weight and mass of an object stay the same when the shape changes.
B) one should work out a strategy before starting on a complex task.
C) an object continues to exist even when one does not see it.
D) a group of people has to take turns talking to one another and then listening.