Because the tenses in B don't make sense. What will his life be? He's dead, nothing will happen, so "will" is not ok here.
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AnonymousWhy is the subjunctive moodIt is applicable, but were after if is not the only case of subjunctive. had been lured is also subjunctive. All past perfect tenses double as past subjunctives. Yoisnot applicable for this sentence?
AnonymousB) what will his life have been if he were not lured into that last, fateful voyagePresent-posterior (will be) doesn't make any sense with past-neutral (note 'last' in that if clause).