Which definition of a use case is true?

A use case is fundamentally a detailed description of how a user interacts with a system to achieve a specific goal. It outlines the steps taken by a user (referred to as a "role") and the system's responses, delineating both the user's actions and the system's outcomes. This interaction is crucial for understanding user requirements and guiding product development or enhancement.

In this context, option C accurately captures the essence of a use case as it focuses on the relationship and interaction between a user and the system, highlighting the sequence of events or actions involved in accomplishing a particular task. This definition is essential in various fields, including software development and business analysis, as it provides a clear framework for identifying functional requirements and user needs.

The other options do not encapsulate the full scope of what a use case represents. For instance, while option A refers to comparing marketing descriptions to a customer's experience, it does not specifically address the structured interaction that a use case entails. Option B focuses merely on the customer’s actions, which is an incomplete portrayal without considering the system’s responses. Meanwhile, option D describes instructions for using software rather than the interactive process that defines a use case. Therefore, the selected answer stands out as the most accurate definition.