Once a credible damage mechanism(s) has been identified, the associated failure mode should also be...

As per API 580, Section 8.3:

“Once a credible damage mechanism(s) has been identified, the associated failure mode should also be identified. For example, local thinning could lead to a pinhole leak in the pressure-containing boundary.”

The example “pit-to-leak” accurately reflects a transition from a damage mechanism (pitting corrosion) to a failure mode (leak). Options B and C are damage modes or mechanisms, and D is a fabrication defect—not a failure mode.