I assume the question creator assumes critical path remains the same until the project manager applies one of the schedule compressing techniques (fast tracking or crashing).
but honestly, I would classify this as a bad question, In the real exam. the question and the requirement will be much clearer.

Below question is from pmstudy.com...

I felt answer is "Choice 2. Decreases by three weeks."... can someone justify why they say cohoce 3 as correct?


Question: You are a principal at an architecture firm which has made you the Project Manager in charge of building four new apartment and office towers on a larger waterfront construction. The project has a critical path of twenty-three weeks. What is the impact on the duration of the critical path if the management wants you to complete the project in twenty weeks?
Choice 1. Increases by three weeks.
Choice 2. Decreases by three weeks.
Choice 3. Remains the same.
Choice 4. Cannot be determined.

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Correct Choice: 3