Which of the following commands can be used to retrieve a Docker secret?

To retrieve a list of Docker secrets, the command used is "docker secret ls." This command effectively displays all the secrets that are currently available in the Docker swarm. It provides a summary including the secret ID, name, and other relevant information, allowing users to see which secrets are stored and available for use.

The other commands listed do not perform the function of retrieving secrets as intended. For instance, "docker secret get," "docker secret show," and "docker secret fetch" are not recognized commands within the Docker command line interface. The functionality to directly retrieve the content of a secret is not handled by the "ls" command; instead, accessing a specific secret’s details typically requires additional steps, including using a service or container that consumes the secret. Therefore, "docker secret ls" stands out as the correct choice for listing the secrets available in the Docker environment.