Which UML diagram can illustrate the relationship between different objects in the system?

The Class Diagram is the appropriate UML diagram for illustrating the relationships between different objects in a system. It provides a clear visual representation of classes, which are blueprints for objects, and their associations, such as inheritance, aggregation, and composition. This diagram allows developers to understand how objects interact with each other and the properties that define them.

Class Diagrams are fundamental in object-oriented design as they help to outline the structure of a system by showing how classes relate to one another. By displaying attributes and methods alongside the relationships between classes, it gives a comprehensive view of the system's design and how various components work together.

Other diagrams, while useful for different purposes, do not focus on object relationships in the same way. For instance, Component Diagrams emphasize the organization and dependencies among software components, Deployment Diagrams show the physical deployment of artifacts on nodes, and State Diagrams model the states of an object as it changes over time based on events. Although all these diagrams are valuable in their respective contexts, they do not specifically capture the direct relationships and interactions between objects like Class Diagrams do.