What defines a class in object-oriented programming?

A class in object-oriented programming serves as a blueprint for creating objects. It encapsulates data for the object and the methods that operate on that data. Essentially, a class defines the structure and behaviors that an object created from it will have. This allows for the creation of multiple instances (objects) of the same class, each with its own set of data, while sharing the same behaviors as defined by the class.

In the context of the other options, a set of functions does not encompass the full definition of a class, as a class is more than just functions—it includes both the data (attributes) and the methods (functions) that operate on that data. A type of variable is too vague, as classes are not simply a variable but a complex structure for creating objects that can have multiple properties and methods. Finally, a collection of data types only focuses on the data aspect without including the associated behaviors or methods that an object can perform, which is crucial to the definition of a class. Thus, identifying a class as a blueprint effectively captures the essential role it plays in object-oriented programming.