Final answer:
The helm command "Nothing to the left" instructs the steersman to neither turn left nor change the ship's course to the left. Its specific direction is to maintain the current course without any leftward adjustments.
Step-by-step explanation:
The helm command "Nothing to the left" is an instruction used in nautical contexts to mean do not turn left or do not change course to the left. It is a directive given to the person steering the ship, indicating that they should maintain their current direction and avoid any leftward movement.
Options c) Alter speed and d) Sound the danger signal is not directly associated with the command "Nothing to the left", as they pertain to the speed of the vessel and safety protocols, respectively, not to directional changes.