1. Identification of Error: Incorrect verb form in a conditional clause expressing a hypothetical or contrary-to-fact condition.
2. Grammatical Rule: For hypothetical or contrary-to-fact conditions in the 'if' clause, particularly when discussing states of being or general hypothetical situations, the subjunctive mood verb 'were' is used, regardless of the subject's number.
3. Option Elimination:
A. Incorrect — uses the indicative 'was' for a hypothetical condition (society is not *solely* structured this way, or it's a theoretical premise), which is grammatically inappropriate here.
B. Correct — 'were structured' properly employs the subjunctive mood for a hypothetical situation that is contrary to fact or a general theoretical premise, aligning with the conditional outcome "would inevitably erode."
C. Incorrect — 'had been structured' uses the past perfect subjunctive, which would typically pair with a main clause like "would have inevitably eroded" (a third conditional). The original main clause, "would inevitably erode," suggests a general or future hypothetical consequence, making the simple past subjunctive 'were' more appropriate.
D. Incorrect — 'would be structured' is not used in the 'if' clause of conditional sentences; 'would' typically appears in the main clause.