The ____ command is used by the superuser, root, to create additional users on the system.

The command used by the superuser, root, to create additional users on a RHEL Linux system is "useradd." This command is essential for system administration tasks, as it allows the root user to add new user accounts and specify various attributes for those accounts, such as the home directory, shell type, and user ID.

When executing "useradd," you can provide options to customize the user creation process. For instance, you can define a specific home directory using the -d option, assign a user to a specific group with the -g option, and more. This flexibility makes "useradd" a crucial command for managing multiple user accounts, which is common in a multi-user environment like a server.

In contrast, the other terms provided do not correspond to standard commands used in RHEL for user management. Therefore, only "useradd" is appropriate in this context for creating new users.