NCLEX Pediatric Growth and Development Practice Test

Independent sitting without support shows that the infant has developed enough trunk and neck control to balance without being held or propped. By about eight months, many babies have the core strength and postural stability to sit upright for extended periods and reach for toys without toppling.

At four to five months, infants typically sit with support or prop themselves up briefly, not yet without help. Fifteen months is much later, aligning with walking milestones, not the ability to sit steadily. So eight months best fits the common pattern of gross motor development for independent sitting.