This question is about identifying the use of the subjunctive mood in English, which is used to express wishes, hypothetical situations, or possibilities. The correct answer is A because it is a classic example of a sentence using the subjunctive mood to express a hypothetical situation. Option B is incorrect because it is a simple present tense statement. Option C is incorrect because it is a future tense statement. Option D is incorrect because it is a present perfect tense statement. The key to this question is recognizing the structure that expresses a situation that is not currently true or real.