What is one example of developmental milestones observed in infants?

Developmental milestones in infants refer to key skills or behaviors that most children typically achieve within a certain age range. One prominent example of such a milestone is rolling over or sitting up unaided. These skills typically emerge within the first year of life and are fundamental to an infant's physical development. Rolling over is usually one of the first signs of developing motor skills, indicating a baby's growing strength and coordination. Similarly, sitting up unaided demonstrates further improvement in balance and core muscle strength.

In contrast, the other options represent skills that either occur at a later developmental stage or are less typical for infants. Reading at an early age generally applies to older children who have developed language and cognitive skills beyond those present in infants. Walking long distances is a skill that develops significantly after infants begin to walk, usually around their first birthday. Lastly, solving complex puzzles is a cognitive milestone that is typically beyond the capabilities of infants, as it requires advanced reasoning and problem-solving skills that develop much later in childhood.