The correct answer is D.
A project manager cannot be responsible for the customer’s inspection process (choice A), only his own. Network diagram changes (choice B) will not affect the root cause of this problem. An apology (choice C) might be in order later, after the root cause is found. The best choice of those provided is to review the Validate Scope process (choice D) as that process deals with acceptance by stakeholders.
Pass PMP in the First Attempt : PMP Strategy
Revise Scope Management Concepts: Project Scope Management
Quiz:
20 Questions Challenge
50 Questions Challenge