What does an activity diagram represent in UML?

An activity diagram in Unified Modeling Language (UML) effectively illustrates the sequence of actions or activities within a process. It is designed to capture the dynamic aspects of a system by showing the flow of control from one activity to another, outlining how tasks are performed and how they interact with each other.

These diagrams are particularly useful for modeling the workflows involving multiple decisions, including branching, concurrency, and synchronization. They provide a visual representation of how activities will occur in various scenarios, helping developers understand and analyze the steps involved in completing a specific process or task. This makes option A the most accurate choice, as it aligns perfectly with the primary function of activity diagrams in depicting workflow and sequence.

In contrast, the other options address different aspects of system modeling. Static relationships between classes relate more to class diagrams, which show how classes interact structurally without focusing on the action sequences. User interactions within the system pertain more to use case diagrams or sequence diagrams, which detail how users engage with the system rather than the activities within processes. Lastly, system deployment architecture is represented through deployment diagrams, which illustrate the physical deployment of artifacts on nodes rather than the sequence of activities themselves. Each of these diagrams serves a distinct purpose within UML, reinforcing why activity diagrams specifically represent