Final answer:
When relieving the helm, the new helmsman should know the ship's position.
Step-by-step explanation:
When relieving the helm, the new helmsman should know the ship's position. This is crucial information for steering the ship in the correct direction. The ship's position is determined using navigation instruments such as GPS, radar, and charts.
The ship's position is essential for maintaining course and avoiding obstacles. If the helmsman doesn't know the ship's position, they may steer the ship in the wrong direction, leading to navigational hazards or deviating from the intended route.
Therefore, option c) ship's position is the correct answer in this context.