Final answer:
The nurse delegate should assign the task of helping position the client who is having a portable x-ray done to the unlicensed nursing assistant.
Step-by-step explanation:
The best nursing task for the nurse to delegate to the unlicensed nursing assistant in this scenario would be to help position the client who is having a portable x-ray done. This task is within the scope of the nursing assistant's training and can be safely delegated. Transporting the client to the Intensive Care Unit via a stretcher and providing discharge-teaching instructions require a higher level of knowledge and expertise and should be performed by the nurse. Assisting the client to go down to the smoking area for a cigarette is not a priority nursing task and should not be delegated to the nursing assistant.