Final answer:
The nurse should respond that the severe burns have damaged nerves that sense pain, causing the lack of pain reporting from the teenage client.
Step-by-step explanation:
The best response by the nurse is C. The severe burns have damaged nerves that sense pain.
Third-degree burns fully extend into the epidermis and dermis, destroying the tissue and affecting the nerve endings and sensory function. These burns are serious and can affect the patient's ability to sense pain. In this case, the teenage client's lack of pain reporting can be attributed to the fact that the severe burns have damaged the nerves responsible for sensing pain.