Final answer:
If the helmsman fails to acknowledge the pilot's steering command and continues on the original course, the correct action to take would be to immediately assume manual control of the wheel (d).
Step-by-step explanation:
If the helmsman fails to acknowledge the pilot's steering command, and continues on the original course, the correct action to take would be to immediately assume manual control of the wheel (d). This means that you would personally take over the steering of the vessel.
As the person on watch, it is your responsibility to ensure the safety of the vessel, and taking manual control of the wheel would be the appropriate action in this situation.