Freya,a 5-Year-Old,is Having Lunch

Freya,a 5-year-old,is having lunch.Her mother pours a tall glass of milk,but Freya objects,saying she hates milk.Her mother then pours all of the milk into a shorter,wider glass,and tells Freya that she can have this instead.This makes Freya happy because she now believes that she has less milk.Freya has not yet mastered the concept of

A) classification.
B) conservation.
C) representation.
D) reversibility.