**Core Concept**: Subjunctive mood requires using 'were' instead of 'was' for hypothetical situations. **Analysis**: - **B** is correct. In hypothetical 'if' clauses, 'were' is standard for all subjects (e.g., 'If I were'). - **A** uses 'was', which is informal and grammatically incorrect here. - **C/D** mix incorrect tenses ('am', 'will be') with 'would', breaking subjunctive structure. **Common Mistake**: Mistaking colloquial usage ('was') for formal grammar.