Final answer:
The best response by the nurse would be to acknowledge the observation and commit to further investigation.
Step-by-step explanation:
The best response by the nurse in this situation would be option c. "Thank you for reporting, I will investigate the observation further."
This response acknowledges the UAP's observation and shows that the nurse takes their input seriously. It also demonstrates the nurse's commitment to further investigating the child's lack of response to questions, which is important for appropriate patient care.