Hi Dear, An MRI is a series of detailed picture of your brain, as they were at the time the MRI was done. They are valid as long as no other changes occur. Basically, if somebody has an MRI today that is normal, and have a stroke or hernia tomorrow, obviously the result will change (You never know).
Undo an action. Press Ctrl+Z or click (Undo) in the ribbon until you've fixed your mistake. You can't undo some actions, such as clicking commands on the File tab or saving a file. If you can't undo an action, the Undo command is dimmed.
sudo is a Terminal command used to execute a command as another user, by default, the root user. This is useful if, for example, a system file or another user's file needs to be edited. sudo will ask for a password, and if successful, will not ask for a password for another 5 minutes. [ edit ].