Which of the following are three types of classes used in a Pega application?

The correct answer identifies three essential types of classes utilized in a Pega application: work class, integration class, and data class.

In Pega, the work class is crucial as it primarily defines the work objects and processes. This class coordinates how cases move through workflows and manage the various states within a business process.

The data class is responsible for managing and defining the data entities required by the application. It specifies the data schema and interactions, allowing the application to handle data storage and retrieval effectively.

The integration class facilitates the interaction between the Pega application and external systems. This is vital for applications that need to communicate with other services, databases, or APIs to enhance their functionality and pull in or send out data as needed.

Together, these classes create a robust structure for developing applications that can efficiently handle business processes and data management. The other options presented do not accurately encompass the foundational classes employed in Pega applications, which is why option B stands out as the correct choice.