A nurse is caring for an 18-month-old toddler who has been hospitalized for 10 days. After the toddler's mother leaves the room, the nurse observes the toddler sitting quietly in the corner of the crib, sucking her thumb. When the nurse approaches the crib, the toddler turns away from the nurse. The nurse should understand that these behaviors indicate which of the following developmental reactions?

A. Regression: The toddler’s thumb sucking, withdrawal, and turning away from the nurse reflect a return to earlier behaviors typically seen in younger children, which is common during stress such as hospitalization. Regression is a coping mechanism when facing unfamiliar or frightening situations. B. Developing autonomy: While toddlers strive for independence, the observed behavior suggests withdrawal and reliance on comfort measures rather than active assertion of autonomy. True autonomy involves exploring and asserting control rather than retreating. C. Separation anxiety reaction: Separation anxiety usually involves crying, searching for the parent, and distress when the parent leaves. The toddler’s quiet, withdrawn behavior is more consistent with coping by regression rather than active protest typical of separation anxiety. D. Resentment toward the mother: There is no evidence in the behavior described that indicates resentment. The toddler’s actions are more indicative of coping with stress and insecurity rather than negative feelings toward the mother.