When are the most expensive defects most likely to be introduced into a product?

Based on my experienced the most expensive defect should be introduced during initial product set-up. It should be identified in FMEA (Failure Mode Error Analysis) here, aside from process failure, critical product defects are identified and introduced with corresponding corrective/ preventive countermeasure

1st option is  C. When the product is being designed.

But, I can't ignore option B (it must be on digital sample).

When the product is being reviewed by the customers. Defects introduced at later stages in the project life cycle are most expensive to fix.

Answer: CExplanation: The most expensive defects are the ones introduced when the product is being designed. This is a little counterintuitive at rst , but it really makes sense once you think about how projects are run. If your team introduces a defect into a product while it's being assembled, then they have to go back and fix it. But if there's a flaw in the design, then you have to halt production and go back and figure out all the things that flaw affected. You may have to order new parts, reassemble components, and maybe even go back and redesign the product from the ground up.