Final answer:
The correct command to log in to a remote image repository in Docker is 'docker login -u username'.
Step-by-step explanation:
The correct command to allow you to log in with the specified username to a remote image repository in Docker is docker login -u username.
For example, if your username is 'johnsmith', the command would be docker login -u johnsmith.
This command prompts you to enter your password after executing it, and once you successfully log in, you can access the remote image repository and perform various Docker operations.