New PMP Question & Answers with explanation

The project management team has determined that there are some changes to the scope of the project. According to the PMBOK, who is responsible for reviewing, evaluating, and approving documented changes to the project?
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If you are working on a project where there is no definite detailed scope, but there are similar projects in the past, what is the correct Estimate Activity Durations tool to use?
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How does time-boxing help minimize scope creep in agile projects?
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Midway through a project, a project manager determined the project was running far behind schedule. If the project manager needs to shorten the project schedule without changing the project scope, which of the following schedule compression techniques could he use?
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Projects operating in agile environments where a high degree of uncertainty exists and where the scope is not yet fully defined, may not benefit from detailed cost calculations due to frequent changes. Instead, lightweight estimation methods can be used to generate a fast, high-level forecast of project labor costs, which can then be easily adjusted as changes arise. Detailed estimates are:
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