1. Identification of Error: Incorrect verb form in a mandative subjunctive clause. 2. Grammatical Rule: The mandative subjunctive requires the base form of the verb in 'that' clauses following expressions of necessity, command, or recommendation (e.g., "it is imperative that," "I demand that"). In a passive construction, this means using "be" + past participle. 3. Option Elimination: A. Incorrect — 'is implemented' uses the indicative mood, which is inappropriate after "it is imperative that" when expressing a demand or necessity. B. Correct — 'be implemented' is the grammatically correct passive mandative subjunctive form, conveying the necessary action. C. Incorrect — 'is to be implemented' indicates a future obligation or plan in the indicative mood, not the mandative subjunctive required by "it is imperative that." D. Incorrect — 'implements' is in the active voice and indicative mood, which is grammatically inconsistent with "policy" as the subject (policies are implemented, they do not implement themselves).