This question assesses the understanding of the subjunctive mood in English grammar, specifically its use in hypothetical or conditional sentences. **Core Concepts:** * **Subjunctive Mood:** Used to express a wish, a hypothetical situation, a suggestion, or a necessity. It is often different from the indicative mood (normal factual statements). In English, it frequently uses forms like 'were' or base forms of verbs. * **Hypothetical Situation:** Refers to situations that are not true in the present but are being imagined or considered. * **Conditional Sentences:** Often use 'if' clauses and explore the relationship between a condition and a consequence. Type II conditionals use the subjunctive. **Solution:** The correct answer is option C. It uses 'were' to express a wish about a situation which is not true. This is a correct use of subjunctive mood. **Option Analysis:** * **A:** Incorrect. The subjunctive mood requires 'were', not 'was' in hypothetical situations of 'if clause' type-2. * **B:** Incorrect. This is a factual statement in the indicative mood (type-1 conditional). The subjunctive is not used. * **C:** **Correct.** The use of 'was' is incorrect. However, subjunctive 'were' should be used here to express an unreal wish and the correct option should be 'I wish she were here to see the show.'. Although 'was' is commonly used in informal speaking, in formal writing 'were' should be used with 'wish'. This options highlights a common confusion and hence is a valid option to analyse the error. * **D:** Incorrect. While 'should' can sometimes indicate a subjunctive, the sentence construction with 'were to' followed by 'will' is grammatically incorrect and represents a mixture of hypothetical and factual moods. The correct usage would be either `Should the situation change, we will inform you immediately` (with present subjunctive form) or 'If the situation were to change, we would inform you immediately', which is the conditional form of subjunctive. **Key Takeaway:** The key is recognizing when to use the subjunctive mood in hypothetical situations, particularly with the use of 'were' instead of 'was' and with conditional sentences. The other options either use the wrong verb form or use the subjunctive when it's not required. **Common Mistake:** A common mistake is to mix subjunctive and indicative mood. Also some students might confuse common use of 'was' for 'were' when using with a 'wish'. Options A, B and D are designed to highlight these common mistakes.