……………. is a summary of scenarios for a single task or goal.Use caseSystem BoundaryClass DiagramUse case Diagram

In this context, the correct answer is "Use case".

A use case is a graphical and textual representation of a system's functionality if the user interacts with it. It provides a summary of scenarios for a single task or goal that details how users will interact with the system to achieve specific objectives. Use cases are crucial in software engineering and system design as they help define the requirements of a system from the end-user's perspective.

Additional options mentioned are relevant as well:

• System Boundary defines the limits of a system, outlining what is included and excluded.
• Class Diagram represents the static structure of a system with classes and their relationships, but it does not focus on user interactions directly.
• Use case Diagram visually represents the relationships between use cases and users, offering a broader view but not as detailed as a written use case.

Thus, the most fitting answer based on the description provided is "Use case".