An administrator wants to add a user named comptia to the system administrators group. Which of the following commands will accomplish this task?

`usermod` is used to *modify* an existing user, not to create a new one. C: `visudo` is used to edit the sudoers file, which controls sudo privileges, not to manage user groups directly. D: `sudo` is used to execute a command with elevated privileges and does not manage user accounts or groups.

The `useradd` command is used to create a new user account on a Linux system. While `-s` is for shell, assuming `-G` is intended for groups from `-sG`, `useradd -G wheel comptia` creates the user `comptia` and assigns them to the `wheel` supplementary group, which is commonly used for system administrators.