During an ad-hoc meeting, the PM notifies the sponsor that while the project is on schedule, material costs have increased and the project is over budget. To save the project, the PM request a material contract with a less expensive vendor. The sponsor approves the change, and project comes in within target tolerances. The company, however, receives numerous stakeholder complaints.
Which of the following is the MOST likely cause of these complaints?

A. The quality of the deliverable decreased due to the rising material cost.
B. The PM did not follow the project communication plan.
C. Quality assurance actions were not adjusted for the vendor change.
D. The change was not documented and approved.