Correct Answer. B. Use a trusted antivirus program to scan and remove the malicious application Utilizing a robust antivirus program to scan for and remove any malicious applications can help restore system stability without the need for more drastic measures such as reinstalling the OS.
Option A is incorrect as defragmentation addresses disk organization, not malicious applications or system security issues.
Option C is incorrect as adding RAM won't solve software-related issues caused by malicious installations.
Option D is incorrect as it should be a last resort after less drastic measures have failed to resolve the issue.