It’s just a flesh wound

Some malware has removed a file association on your Windows 7 computer. Now that the malware has been removed, which of these would be the best way to restore this file association?

A) Change the compatibility mode for the application

B) Update the Control Panel / Default Programs

C) Change the file extensions

D) Modify the registry settings for those file types

E) I’m sure they’ll go back to normal on their own