The correct line to add is john ALL=(ALL) NOPASSWD: /bin/systemctl restart httpd. This allows the user john on all hosts (ALL) to execute the specific command /bin/systemctl restart httpd without being prompted for a password (NOPASSWD:). The ALL=(ALL) allows execution as all users and groups, although in this case, the specific command does not require changing to a different user or group. It's important to use full paths for commands in sudoers for security. The other options are incorrect because they either omit NOPASSWD: which would still prompt for a password, use ALL which would undesirably allow all commands, or specify an incorrect command path.