Correct Answer: BUpdating the business case as part of 'managing a stage boundary' involves ensuring the project remains viable and justifiable. This includes revising the overall plan and resources to complete the project based on the actual progress, costs, and resource usage from the preceding stage. By doing this, it maintains the accuracy and relevance of the business case and ensures the project still aligns with its intended benefits and objectives. Therefore, the project manager should revise the overall plan and resources to complete the project, based on actuals from the stage 3 plan.