Final answer:
Administer a normal saline solution temporarily.
Step-by-step explanation:
If the bag of IV solution is empty and the nurse is waiting for a new bag, the best temporary solution is to administer a normal saline solution (option D) to the client. Normal saline is an isotonic solution that closely approximates the electrolyte composition of body fluids, making it suitable for intravenous administration. This will help maintain the client's fluid and electrolyte balance until the new bag of PN solution arrives.