Alice is sitting at the table with her son Nikko. She takes his tall glass of milk, and pours exactly half of it into a shorter wider glass. Then she says "Honey, which glass has more milk?" Nikko immediately points to the taller glass

Nikko has not yet mastered Piaget's skill of _____________.
A) centration
B) egocentrism
C) object permanence
D) conservation

Answer: D
Rationale: Conservation is the knowledge that the quantity or amount of an object is not related to the physical arrangement and appearance of that object. In this example, Nikko does not understand that pouring fluid into different containers does not change the actual amount of fluid. This is a classic example of conservation (or the lack thereof).