Final answer:
The statement is true; activity diagrams help in developing system sequence diagrams by providing an overview of the system's behavior and ensuring consistency with SSDs.
Step-by-step explanation:
The statement that activity diagrams are helpful in developing system sequence diagrams (SSDs) is true. Activity diagrams provide a broad overview of a system's behavior by showing the sequence of activities and the flow of control from one activity to the next. They are often used to capture the dynamic aspects of a system. An SSD, on the other hand, is a more focused diagram that shows the interactions between an actor and the system in a specific use case. By using an activity diagram, a designer can first understand the overall flow of the system and then distill this into the more concentrated interactions found within a system sequence diagram. This helps ensure that the interactions in the SSD are consistent with the larger system behavior captured in the activity diagrams.