According to Piaget's Observations, Most Children in the Transitional Stage

According to Piaget's observations, most children in the transitional stage for developing conservation of volume:

A) usually traverse this stage at age 2.
B) usually traverse this stage at age 8.
C) are still unaware that they need to consider both the height and the width of the container.
D) know that height and width are important but have difficulty keeping both in mind simultaneously.