Here is my opinion:
A) determine if the cost of the product will meet budget requirement -- This is normally done in the planning stage

B) Persuade management to invest in quality product methods - I guess this is done before project starts so that budget can be allocated for quality or after completion of the project to showcase the advantages of adhering to the quality methods. Remember Org. process assets are updated after quality assurance stage so that current and future project can implement the best quality practices.

C) Access the cost of implementing quality improvements : Looking at cost of quality means makes sure that project is not spending too much money on the quality. So in quality assurance stage, you are inspecting if the deliverable is meeting the customer reqirements and if not how to implement the required changes provided you do not over spend your money on quality. So I think this is the best option.

D) determine most cost effective approach when considering prevention, inspection and repair: This is normally done in the planning stage

what's the correct answer and justification given?