When Should You Use Dialog Boxes (Alert, Confirm, and Prompt)

When should you use dialog boxes (alert, confirm, and prompt) for input and output?

A) Dialog boxes are new with HTML5 and, as such, they are gaining traction as the preferred technique for all input and output.
B) Use dialog boxes only when you want to draw sharp attention to something and you want to force the user to deal with the issue immediately.
C) Use dialog boxes for all text input, but not for numerical input.