This question assesses understanding of subjunctive mood usage. The subjunctive mood is used to express hypothetical situations, wishes, or demands. Option D correctly uses the subjunctive ‘go’ after ‘suggested,’ a verb that often takes the subjunctive. Option A uses 'was' incorrectly; in the subjunctive it would be 'were.' Option B uses past perfect 'has been' incorrectly as it refers to something that has happened instead of a hypothetical. Option C while commonly used in informal speech is in the indicative mood, not the subjunctive. Therefore, the correct answer is D. **Core Concept:** Subjunctive Mood Usage. **Solution Analysis:** The subjunctive mood is used for hypothetical scenarios. Option D uses the subjunctive form correctly, while other options present typical errors. **Option Analysis:** - **A. If I was you, I would accept the offer.:** Incorrect subjunctive. Should be 'If I were you.' - **B. If he has been there, he would have seen it.:** Incorrect as it uses past perfect in place of the subjunctive - **C. I wish she was here.:** Indicative mood, not subjunctive, should be I wish she *were* here. - **D. He suggested that she go to the library.:** This correctly employs the subjunctive, particularly after 'suggest.' **Common Mistake:** Confusing the indicative and subjunctive mood, or thinking ‘was’ is appropriate in hypothetical ‘if’ clauses.