Correct Answer to Q#80: D
Unless stated differently, on agile projects the cost and the schedule are fixed, while the scope is flexible. Therefore, meeting with the product owner to discuss the scope reduction, or in other words, to re-prioritize the backlog, is the best option among the answer choices provided.
Exam Reference: Exploring Scrum: The Fundamentals, 2nd Edition, Dan Rawsthorne with Doug Shimp, 2013, Reprioritization of Requirements