Which UML diagram shows the interaction between objects over time ?

The correct answer is Option C, the Sequence diagram. A Sequence diagram is a type of interaction diagram in UML that specifically illustrates how objects interact with each other over time. It arranges object lifelines vertically and displays messages exchanged between them horizontally, ordered chronologically from top to bottom. This temporal ordering makes it the ideal choice for visualizing dynamic behavior and message flow.\nIn contrast, a Class diagram (Option A) is a static structural diagram that shows the system's classes, attributes, and relationships without depicting time-based interactions. A Use case diagram (Option B) captures functional requirements from a user's perspective, focusing on actors and system functions rather than object interactions. An Activity diagram (Option D) models the flow of control or data within a system, similar to a flowchart, but does not emphasize object interactions over time in the same way. Therefore, only the Sequence diagram explicitly addresses the interaction between objects across a timeline.