The correct answer is B. The agent is grounded on a Knowledge data library, and the goal is broad FAQ coverage without manually writing every test. Agentforce Testing Center can generate test scenarios directly from the knowledge sources available to the agent, which makes it the best fit for building an initial regression suite quickly. Option A is valid only when the team already has prepared test cases, but the scenario says manual authoring would take too long. Option C can test routing and tool selection based on subagents and actions, but it does not directly exploit the 200 FAQ articles as the source for test coverage. For knowledge-grounded agents, generating test cases from available Knowledge content is the efficient and relevant approach.