In Piaget's Concrete Operational stage, children develop the ability to:

In Piaget's Concrete Operational stage, which typically occurs between the ages of 7 and 11, children gain the ability to think logically about concrete events. This stage is characterized by the development of skills such as classification and conservation, as well as the ability to perform operations that can be reversed.

The correct choice highlights the ability to classify objects into different sets and recognize relationships among those sets. For example, a child can understand that a dog is also an animal, and they can classify animals into various categories based on shared characteristics. Additionally, the ability to reverse logical operations means that children can understand that if they pour water from one container to another, they can also pour it back and recognize that the volume remains the same.

This operational thinking is grounded in tangible, practical experiences rather than hypothetical or abstract concepts, which distinguishes it from other stages of cognitive development where more complex reasoning might be introduced.