Here is a tip:
Baseline of the project is used as a benchmark to determine the progress of the project.

Explanation
Changes in baseline are avoided due to its impact of tracing errors and other processes as the project progresses.

Under following conditions, changes in baseline can be made:

Failure of project: When a project cannot achieve its objective, then changes can be made in the baseline.
Improvement: When there are certain areas in which project can be improved, then changes can be made in the baseline.
Natural disaster: The natural and unavoidable causes will change the baseline.
Under following conditions, changes will not be made in the baseline:

Improve performance of the project: Minor changes in cost and plans that can enhance the scope of performance of the project will not be done to change the baseline.
After completion of cost accounts: Once the cost accounts are completed, the baseline could not be changed.
Verified Answer
The project managers avoid making changes to the project baseline as the monitoring and tracking process of the project can be impacted negatively and it may lead to further delay.

Changes to the project baseline becomes necessary when there is:

Failure of project
Improvement
Natural disaster
Changes to a baseline are not allowed under following situations:

Improve performance of the project
After completion of cost accounts