Final answer:
The command to turn the ship's wheel completely in one direction at sea is 'hard a-port' for left or 'hard a-starboard' for right. The correct answer is 'a. hard'.
Step-by-step explanation:
At sea, if you want the wheel turned all the way in one direction, the four-letter word you say is "hard". Therefore, the correct answer to the question is "a. hard" for either "a-port" or "a-starboard", indicating a full rudder turn in the desired direction. This is a common nautical term used to instruct a helmsman to turn the ship's wheel as far as it can go in a direction.
For example, the command "hard a-port" would mean to turn the wheel completely to the left side of the ship. Conversely, "hard a-starboard" means to turn it completely to the right side. This command is used to make quick and sharp turns, often to avoid immediate dangers or when maneuvering in tight situations at sea.