Final answer:
Activity diagrams are indeed helpful for visualizing complex workflows or activities within a system, allowing for clearer analysis and communication of system processes.
Step-by-step explanation:
The statement activity diagrams are helpful when the flow of activities is too complex is True. Activity diagrams are a type of UML diagram that are particularly useful for modeling the workflow or the activities involved in a system. These diagrams are helpful in understanding and communicating how a system works, especially when dealing with complicated processes where multiple paths and outcomes need to be considered. By charting the activities and decisions, these diagrams assist in visualizing the sequencing of activities, which is crucial for the analysis and design of a complex system.