Final answer:
The nurse should perform action C first, which is sponging the client while monitoring for shivering. After that, the nurse should monitor the client's temperature more often than ordered.
Step-by-step explanation:
The nurse should perform action C first, which is sponging the client while monitoring for shivering. Sponge baths with cool water can help lower the client's temperature. The nurse should monitor for shivering because shivering is the body's way of generating heat to increase body temperature. By monitoring for shivering, the nurse can ensure that the client's body temperature doesn't drop too low.
After performing action C, the nurse should then monitor the client's temperature more often than ordered (option B). This will help the nurse assess the effectiveness of the sponging and determine if any additional interventions are necessary.
Actions A and D can be considered once the nurse has taken the initial steps of sponging and monitoring the client's temperature. These actions provide additional cooling measures to help reduce the client's high temperature.