Dana Presents a Child with Two Identical Balls of Clay

Dana presents a child with two identical balls of clay.She rolls one of the balls into a long,thin piece of clay.She then asks the child if there is more clay in the ball or in the long,thin piece.The child replies that both have same amount of clay.According to Piaget's stages of development,the child's reply indicates that the child is capable of:

A) concrete operations.
B) formal operations.
C) inference operations.
D) judgment operations.