What is an example of a developmental milestone in early childhood?

Walking independently by age one is considered a key developmental milestone in early childhood because it signifies a crucial stage in a child's physical development and overall growth. This milestone demonstrates a child's increasing motor skills, balance, and coordination, which are essential for further physical activities and exploration of their environment.

Typically, children begin to walk independently around their first birthday, although there's a range of normal development, with some children walking earlier or later. Achieving this milestone allows children to gain more independence, develop confidence in their abilities, and explore their surroundings, which can foster cognitive, social, and emotional development. It lays the foundation for other skills, such as running, climbing, and engaging in more complex play activities.

The other scenarios presented do not align with typical developmental timelines, as learning to read before age 5, writing full sentences at age 3, and solving complex math problems at age 4 are not common developmental milestones for those age groups. These skills generally emerge later as children progress through their learning stages.