2.2.2.1-12 Option Display Dependent on Context

Menus should display as selectable only those options that are actually available in the current context.

Additional Information:
If a user selects a displayed option, and is then told that option is not actually available, an undesirable element of unpredictability has been introduced into the interface design. Users may become uncertain and confused about command entry. There should be some indication of which options are currently available; see Guideline 2.2.2.5-8.