Luis watches his mother open two equal containers of milk and pour each container of milk into a glass. She pours one container of milk into a glass that is short and wide, while the other glass is tall and thin. Although both glasses contain the same amount of milk, Luis wants the tall, thin glass because he says it has "more milk.". Luis is

a. unable to demonstrate egocentrism.
b. unable to demonstrate object permanence.
c. developmentally delayed in his cognitive development.
d. unable to make a transformation.

D