The mother of a 4-month-old baby girl asks the nurse when should she introduce solid foods to her infant. The mother states, "My mother says I should put rice cereal in the baby's bottle now. The nurse should instruct the mother to introduce solid foods when her child exhibits which behavior?

A. Opens mouth when food comes her way: Readiness for solid foods is indicated by developmental cues, such as the infant showing interest in food and opening her mouth when offered. This usually occurs around 4–6 months of age and signals that the infant can begin exploring solids safely. B. Stops rooting when hungry: Rooting is a reflex that helps the infant find the nipple for breastfeeding or bottle-feeding. Its cessation is not a reliable indicator of readiness for solids and does not guide the timing of introducing solid foods. C. Gives up a bottle for a cup: Transitioning from bottle to cup occurs later in infancy, usually around 6–12 months, and is not a developmental milestone for starting solids. D. Awakens once for nighttime feedings: Nighttime sleep patterns reflect sleep development rather than readiness for solid foods. This behavior does not indicate that the infant can safely start solids.