Object permanence is best described as:

Object permanence is best understood as the awareness that objects continue to exist even when they cannot be seen, heard, or otherwise sensed. This concept is integral to cognitive development, particularly as outlined by Jean Piaget, who proposed that infants develop this understanding as they progress through their early stages of life.

When an infant lacks object permanence, they may believe that an object ceases to exist once it is hidden. For example, if a toy is placed under a blanket and the infant has not yet developed object permanence, they may not look for it because they think it is gone. This realization typically develops around 8 to 12 months of age, marking a critical stage in cognitive growth and the way children interact with their environment.

The other options, while relevant to cognitive processes, address different aspects. Recognizing that physical properties do not change refers more to understanding concepts of conservation, while categorizing objects relates to classification skills. The capacity to remember previously observed objects emphasizes memory but does not specifically address the continuity of existence when such objects are not visible. Thus, option A clearly captures the essence of object permanence.