Which of the following concepts describes the ability to reverse operations or actions mentally?

The concept that describes the ability to reverse operations or actions mentally is indeed reversibility. This cognitive skill, often discussed in the context of Piaget's stages of cognitive development, refers to the understanding that certain actions can be undone or reversed, returning to the original state. For example, if a child sees that water can be poured from a tall, narrow glass into a short, wide glass and understands that if the water is poured back, it will return to its original container, they are demonstrating reversibility.

This understanding is crucial for several mathematical concepts, such as addition and subtraction, where one operation can reverse another (for example, 5 + 3 can be reversed to find 3 + 5). In essence, this cognitive ability allows individuals to comprehend that certain processes can be undone, facilitating more advanced reasoning and problem-solving skills.