A child begins to pull toys from her toy box, and, in so doing, she sorts them into separate piles of cars, trucks, and animals. She also understands that some toys can be switched from one pile to another or can form new piles based on subtypes having similar colors. This behavior is called and is characteristic of the concrete operational stage of development.

classification

Explanation:

Classification operational stage of development -

In this stage of development , the children tends to learn the difference and similarities between certain objects , is referred to as the classification stage .

This stage starts in the age 7  to 11 , and the mind of the child develops further , by learning this classification .

Hence , from the given scenario of the question ,

The correct term is classification .