A quarter of way through development of the project, you realize the main component has been left out of project specification. Business unit should be notified and should agree to changes in project specification.
When you (as Project Manager) explain this to a business unit manager in hallway, he publicly blames you for not doing job right. Write down dialog which would happen at team meeting as you explain process you would use to deal with this situation. Make sure to write ideas for managing expectations and steps one can utilize to manage angry people.