During the concrete operational stage, which typically occurs between the ages of 7 and 11, children demonstrate significant advancements in cognitive abilities. One key aspect of this stage is their understanding of conservation. This refers to the realization that certain properties of objects, such as volume, mass, and number, remain constant despite changes in form or appearance. For example, children in this stage can recognize that pouring liquid from a tall, narrow glass into a short, wide glass does not change the amount of liquid.
Additionally, children begin to grasp basic mathematical concepts, such as addition, subtraction, and understanding simple relationships between numbers. They can categorize objects and logically organize information, which enhances their problem-solving skills, though these skills are generally still tied to concrete situations rather than abstract thought.
The other options reflect skills that develop either later in childhood or are not specific to the concrete operational stage, making the understanding of conservation and basic math the definitive hallmark of this developmental stage.