A nurse is caring for a client who has dementia and insists that a doll is their infant child. Which techniques should the nurse use when interacting with the client?

The correct answer is C: Validation therapy. This technique involves acknowledging and validating the client's feelings and reality without challenging them. It helps build trust and rapport with the client, reduces agitation, and promotes a sense of security. Cognitive reframing (A) involves changing negative thought patterns, which may not be effective in this scenario as the client's belief is deeply rooted. Thought stopping (B) is a cognitive-behavioral technique to interrupt negative thoughts, not suitable for this situation. Operant conditioning (D) uses reinforcement to modify behavior, which is not appropriate for addressing the client's perception of the doll as their infant.