Final answer:
A sailor must carry a specimen cup above their eye level to keep it in sight of the observer at all times.
Step-by-step explanation:
In order to keep a specimen cup in sight of an observer at all times, a sailor must carry the cup in a position above their eye level, such as on top of their head or held high above their head. This ensures that the cup remains visible even when the sailor is moving or the observer's line of sight is obstructed by other objects.