Final answer:
The boxes on a class diagram can be thought of as a set of objects. Hence the correct answer is option 3
Step-by-step explanation:
The correct answer is 3) set of objects.
The boxes on a class diagram in computer science can be thought of as a particular set of objects. A class diagram is a visual representation of the classes or objects in a system and the relationships between them. Each box on the class diagram represents a class or an object, which is a specific instance of a class.
For example, if we have a class diagram for a banking system, the boxes on the diagram could represent objects like Account, Customer, Transaction, etc. These objects have attributes and behaviors as defined by their corresponding classes.