Which type of diagram shows the relationships between classes in object-oriented design?

A class diagram is a fundamental part of object-oriented design that visually represents the structure of a system by showing the system's classes, their attributes, methods, and the relationships between the classes. It helps to capture the static aspect of the system and is essential for understanding how different objects within the system interact with one another.

Class diagrams define the blueprint for the classes that will be implemented in the software, illustrating how they are linked through associations, dependencies, inheritances, and other relationships. This information is crucial when designing the architecture of a system, as it allows developers to understand how to organize the code and how different parts of the system communicate with each other.

In contrast, flowcharts represent processes or workflows rather than classes and their relationships. Use case diagrams focus on the interactions between users (actors) and the system to achieve specific goals, emphasizing the behavior of the system rather than its structure. Entity-relationship diagrams are tailored for database design, capturing data points and the relationships between them rather than object-oriented classes. Thus, among these options, the class diagram is the specific diagram that accurately represents the relationships between classes in object-oriented design.