Which node marks the end of concurrent sequences in an activity?

Which node marks the end of concurrent sequences in an activity?

• A. Merge node
• B. Join node
• C. Fork node
• D. Decision node

Answer: (A)

The key idea is how activity diagrams handle parallel work and its completion. After a flow splits into parallel paths with a fork, the sequence is considered finished when those parallel tasks are all done. A join node is what coordinates this: it waits for every incoming parallel branch to complete and then merges them back into a single flow, marking the end of the concurrent section. The merge node, by contrast, brings together alternate paths that could result from a decision, not the synchronization of parallel threads. A decision node chooses which path to take based on a condition, and a fork node starts parallel execution. So, the end of concurrent sequences is indicated by the join node.

The key idea is how activity diagrams handle parallel work and its completion. After a flow splits into parallel paths with a fork, the sequence is considered finished when those parallel tasks are all done. A join node is what coordinates this: it waits for every incoming parallel branch to complete and then merges them back into a single flow, marking the end of the concurrent section. The merge node, by contrast, brings together alternate paths that could result from a decision, not the synchronization of parallel threads. A decision node chooses which path to take based on a condition, and a fork node starts parallel execution. So, the end of concurrent sequences is indicated by the join node.