Where do you find actors?

Actors are found in both swim lane diagrams and use case diagrams, making option B the accurate answer.

In the context of business analysis, an actor represents a role that interacts with the system being modeled. In use case diagrams, actors are essential because they help to identify who will engage with the system, whether it's users, other systems, or external entities. This relationship illustrates the functionality required from the system's perspective.

Swim lane diagrams also depict actors by organizing the various tasks and processes into lanes associated with specific roles or departments. This organizational structure clarifies responsibilities and interactions, further emphasizing the role of actors in the workflow.

The other options do not correctly represent the typical locations of actors. For instance, class diagrams focus on the structure of classes and their relationships, rather than the interactions with roles. Formal necessity specifications concentrate on requirements without specifying the roles involved in interacting with a system. Business requirement documents capture the needs of the business but typically do not articulate the specific actors involved in the processes. Thus, option B clearly captures where actors can be found in the modeling of systems.