Final answer:
The most helpful assessment question in determining the cause of the client's complaints is "Has anything caused you to change your usual routine lately?"
Step-by-step explanation:
The question is asking which assessment question would be most helpful in determining the cause of a client's recent restlessness and increased irritability. From the given options, the most appropriate assessment question would be B. "Has anything caused you to change your usual routine lately?" This question focuses on external circumstances that might have triggered these complaints, which could provide valuable information about the cause. By understanding any recent changes in the client's routine or environment, the healthcare professional can gain insight into potential stressors or triggers for the restlessness and irritability.