Final answer:
The nurse is using the pain management technique of distraction by playing music for the child with leukemia.
Step-by-step explanation:
The pain management technique being used by the nurse is distraction. Distraction involves redirecting a person's attention away from the pain by engaging them in an enjoyable or interesting activity. In this case, the nurse is playing music for the child with leukemia, which can help to divert the child's attention and reduce their perception of pain.