WHy is b not correct answer and c correct answer

A customer in the latter part of project execution wants to add scope to the project. The project manager discusses this change with the customer and raises a written change request. He then evaluates if this change can be addressed through project reserves and explores alternatives. The project manager finds that this addition would result in missing the next milestone delivery of the project. What should the project manager do NEXT?

a) Evaluate the impact of the change on other factors of triple constraint - cost and time
b) Perform Integrated Change Control
c) Get an approval from the Change Control Board
d)Update the project baseline and inform the customer

Explanations:

Answer (c) Get an approval from the Change Control Board. Since the project affects the milestone deliverable, it is best to gain approval from the change control board. The board would have the responsibility to review change requests to determine if additional analysis is warranted. They can also approve or reject project changes. The change control board can include the project sponsor, customer, experts, and others besides the project manager