Final answer:
The nurse should report the situation to the nurse manager and ensure patient safety.
Step-by-step explanation:
The nurse should take action and report the situation immediately to the nurse manager (C). The nurse has a duty to ensure the safety and well-being of patients and alerting the nurse manager about the drowsy nurse is the appropriate course of action. Leaving the nurse alone to sleep (D) should not be done since it could jeopardize patient care. Filling out an incident report (B) may be necessary if any unusual occurrences were observed, but it is not the primary action to address the situation. And although the state's board of nursing handles discipline (A), it is still important to report the situation to the nurse manager.