Under what circumstances is it OK for a product owner to substitute one user story for another one during a sprint?

1. When the team unanimously agrees during a daily scrum

2. When the product owner overlooked a functional requirement that must be in the next release

3. When the effort required for the new user story is the same as the old one

4. When the product owner receives an urgent request from a stakeholder

5. It is never good practice to add work items to the current sprint