The requirement is to establish a network security boundary around a specific service (BigQuery) for resources in a Folder, while allowing the team to manage that boundary. This is the definition of using VPC Service Controls (VPC SC) with scoped policies.
VPC Service Controls (VPC SC): Used to create a service perimeter (a security boundary) around BigQuery and other Google Cloud services, which restricts API access.
Scoped Policy on the Folder: This enforces the boundary exactly at the required Folder level, as opposed to the organization level.
Access Context Manager Editor Role: Access Context Manager is the service that manages VPC SC policies (Service Perimeters and Access Levels). Granting this role on the scoped policy allows the data analytics team to fulfill the requirement to "control the restrictions." Extracts (Conceptual Basis for VPC SC and Scoped Policies):
"Private Service Connect provides... Explicit authorization. Private Service Connect provides an authorization model that gives consumers and producers granular control, ensuring that only the intended service endpoints and no other resources can connect to a service." (Source 2.4 - VPC SC and PSC share a core architectural concept of explicit, service-oriented boundaries) Option B is the technical implementation that matches the requirements: using a VPC SC service perimeter (for service restriction) applied as a scoped policy on the folder (for resource hierarchy scope) with Access Context Manager Editor (for team management/control).