Error, fault, failure is the option that describes the causal chain in the correct sequence1 . The causal chain is a model that explains how defects are introduced and manifested in software1 . An error is a human action or decision that produces an incorrect result1 . A fault is a defect in the software caused by an error1 . A failure is an incorrect behaviour of the software caused by a fault1 . The other options do not describe the causal chain in the correct sequence. Option B uses synonyms for error (mistake), fault (bug), and failure (defect), but does not follow the correct order. Option C uses synonyms for error (mistake) and fault (failure), but does not follow the correct order and confuses fault with failure. Option D uses synonyms for fault (bug) and error (error), but does not follow the correct order and confuses failure with error.