Final answer:
The nurse demonstrates the ethical principle of veracity when providing accurate information to a patient about their diagnosis.
Step-by-step explanation:
The nurse demonstrates the ethical principle of veracity in situation 1, which is providing accurate information to a patient about their diagnosis. Veracity refers to honesty and truthfulness, and in this situation, the nurse is being honest with the patient by sharing accurate information about their health condition. Administering medication without informing the patient (situation 2), withholding information about treatment options (situation 3), and ignoring a patient's request for information (situation 4) do not demonstrate the principle of veracity, as they involve dishonesty or withholding information.