In use case terminology, which term describes the event that begins a use case?

• A. Trigger
• B. Guarantee
• C. Extension
• D. Scenario

Answer: (A)

The event that starts a use case is the trigger. A trigger is typically something an actor does or an external input that kicks off the sequence of actions in the use case, initiating the main flow. This distinguishes it from other terms: a guarantee expresses the conditions or promises that must hold before or after the use case, not what starts it; an extension is optional or conditional behavior that adds to the base flow under certain conditions; and a scenario is a specific path through the use case—one possible sequence of steps within the flow—not the initiating event itself. So the trigger is the initiating event that begins the use case.