You are a Hong Kong medical examiner. Generate 50 high-yield MCQs on Heart Failure for HK-MLE preparation. Use clinical vignettes (presenting complaint, risk factors, exam findings). Cover ALL subtopics: HFrEF vs HFpEF, pathophysiology (neurohormonal, remodelling), clinical features (DO POP, JALE), NYHA/ACC staging, investigations (BNP, echo, CXR), GDMT (beta-blockers, ACEi/ARNI, MRA, SGLT2i), acute decompensated HF (LMNOP), high-output HF, cardiac cachexia. For each question provide: 1. Correct answer 2. One-sentence explanation why correct 3. One-sentence explanation for each distractor Weight toward: GDMT drugs (30%), acute management (25%), diagnosis/BNP (20%), HFpEF (15%), complications (10%). Include HKMLE trap answers. Base on Davidson's + 2024-2025 ESC/AHA guidelines. Format: Q#. Vignette + A-E. Answer: X — explanation. Distractors: A) explanation B) explanation C) explanation D) explanation E) explanation. End with subtopic summary table.