How can you push a Docker image to a registry?

To push a Docker image to a registry, the correct command is docker push [image_name]. This command is specifically designed to upload a locally built Docker image to a remote Docker registry, such as Docker Hub or a private registry. When using docker push, you ensure that the image, along with its tags, is sent to the specified registry, making it accessible for others to pull and use.

The other choices presented do not serve the purpose of pushing images to a registry. For instance, registering an image is not a valid command in Docker, and the terms 'pull' and 'upload' are associated with different functionalities: docker pull [image_name] is used to download an image from a registry to your local machine, whereas docker upload [image_name] is not a recognized Docker command at all. Thus, using docker push is the appropriate method for this task, aligning perfectly with the functionality described.