A question on Cost of Quality

[b]Which of the following is also known as failure costs?[/b]

A>Cost of poor quality
B>Internal costs
C>Prevention costs
D>Cost of defects

I need to know the explanation of the answer. The ans as per one of the education provider is : A

My question is why it is not D? Is Defect not a failure? why will the cost of defect will not come under failure cost? Defect will require Rework and that is under failure costs.

it is cost of poor quality.

as defect means there was not a problem with plan but the deliverable may be say was built wrong.

it is not necessary that always defect will have a cost related we could have made adjustments also right?

It is ans 'A'.

Ref: PMBOK Page No: 235 under "Quality Management"

Cost of Non conformance >Internal failure cost (Plan Quality management page 235 PMBOK 5th ed)

Rework
Scrap

Rework can be done because of Defects right? then Cost of defect can be a internal failure cost.

Please explain what is wrong with my understanding.