What is the BEST alternative if you discover that a rootkit has been installed on...

Rootkits can deeply infect and compromise a system’s kernel, making them very difficult to detect or remove fully. Even advanced antivirus solutions may miss them.

The most secure and recommended response is:

Completely wipe the compromised system.

Reinstall the OS from known good (clean) media.

Apply all patches and updates.

From CEH v13 Official Courseware:

Module 6: Malware Threats → Rootkit Handling

Incorrect Options:

A: Copying files might transfer infected components.

B: Trap and trace is investigative, not remedial.

C: Deleting files may not fully remove the rootkit.

D: Backups might be infected if taken post-compromise.