The following sentence has been split into four segments. Identify the segment that
contains an error.
If he had paid / attention to the announcement, / he had not / missed the train.

Correct option is B

The use of "had not" is grammatically incorrect in the context of a third conditional sentence. The correct form "would not have" properly indicates a hypothetical situation in the past that did not occur.
· Grammatical rule used: Third conditional sentences use the past perfect tense in the 'if' clause and 'would have' + past participle in the main clause.
· Example: If it had rained, we would have stayed home.