What command is used to pull an image from a Docker registry?

The command used to pull an image from a Docker registry is "docker pull [image_name]." This command specifically instructs Docker to retrieve an image from a specified registry, which is typically Docker Hub by default, although it can be pointed to other registries as well.

When you use the "docker pull" command followed by the image name, Docker checks the local image cache to see if the image is already available. If it isn't found locally, Docker then contacts the registry, downloads the specified image, and saves it on your local machine. This functionality is crucial for working with Docker, as it allows users to access and utilize prebuilt images for their applications, ensuring they have the necessary software stack ready to run containers.

The other options do not represent valid Docker commands for this purpose. For instance, "docker fetch" and "docker download" are not recognized Docker commands. Similarly, "docker get" does not exist in the Docker command set and does not represent the action of retrieving an image from a registry. Hence, "docker pull [image_name]" is the correct choice because it accurately describes the command used to pull down a Docker image from a registry.