Question

viruses temporarily erase their code from the files where they reside and then hide in the active memory of the computer. polymorphic stealth encryption multi - partite i dont know yet

Explanation:

Stealth viruses use techniques like temporarily removing their code from infected files and hiding in active memory to avoid detection by antivirus software. Polymorphic viruses change their code structure, encryption viruses use encryption for their payload, and multi-partite viruses infect both files and boot sectors—none match the described behavior except stealth viruses.

Answer:

Stealth