A project manager led a hybrid project under a time-and-materials contract. After delivery and client acceptance, the client returned one week later asking to fix two defects. The project manager provided a time and cost estimate and asked the client to confirm, but the client insisted the fixes should be free. What should the project manager have done to prevent this?

The correct answer is "Planned how the delivered product will be supported after its delivery." This is a crucial aspect of project closure and ensures that post-delivery responsibilities are clear. By planning for product support, the project manager could have established a formal process for handling defects, including timelines, costs, and who is responsible, preventing the client's expectation of free fixes. "Train client engineers to support the product after delivery" is a possible solution but doesn't address the immediate issue of defects or the contractual obligation. "Review the project's quality control plan with the client" is important during execution but doesn't define post-delivery support terms. "Propose a fixed-price contract that included one month of free bug fixes" is a different contractual model and a reactive solution; the issue here is the lack of a support plan for the existing contract type.