Which command displays the list of groups to which a user belongs?

`whoami` only prints the effective username of the current user and provides no information about group membership.

`lsgroup` is not a standard Linux command and does not exist as a built-in utility.

`who` shows which users are currently logged into the system and their login sessions, not group membership details.

The `id` command prints the real and effective user ID (UID), primary group ID (GID), and the full list of all supplementary groups the user belongs to. Running `id username` for a specific user or `id` alone for the current user provides complete group membership information. This makes it the definitive command for answering questions about group membership on Linux systems.