Which UML diagram would you use to represent the flow of activities in a system?

An Activity Diagram is specifically designed to depict the flow of activities within a system. It allows for visual representation of the sequence of steps or actions involved in a process, showcasing how different activities are linked and how they transition from one to another. This diagram focuses on the dynamic aspects and emphasizes the workflow or process, which makes it particularly useful in modeling business processes, algorithms, or detailed system behaviors.

In contrast, the other types of UML diagrams serve different purposes. A State Diagram captures the states of an object and the transitions between those states, focusing on the life cycle of a particular object rather than the flow of activities. A Component Diagram illustrates the organization and dependencies among components in a system, showing how they interact but not detailing the specific activities within a process. An Object Diagram provides a snapshot of the instances of classes, focusing on their attributes and relationships at a specific time rather than the flow of activities over time. Hence, the Activity Diagram is the most appropriate choice for representing the flow of activities in a system.