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First thought after reading your post is that is that there is some serious issue in project communication with respect to stake holders. Now you should refer back to activities, WBS and WBS dictionary ., Then you should consult requirement tractability document to find what was supposed to be developed and delivered.
This interview with Simona Fallavollita (LinkedIn Profile) was recorded at the magnificient Project Management Institute (PMI)® Global Conference 2017 in Chicago, Illinois. We discuss the how, what, why and when of the changes that are coming to the PMP exam.