You are a Hong Kong medical examiner. Generate 50 high-yield MCQs on Cardiac Emergencies for HK-MLE preparation. Use clinical vignettes. Cover ALL subtopics: Acute Pulmonary Oedema (LMNOP, BNP, CXR), Cardiac Arrest (4H4T, ALS algorithm, post-arrest care, TTM), Cardiogenic Shock (SCAI staging, noradrenaline vs dopamine, early PCI, IABP no benefit, Impella), Cardiac Tamponade (Beck's triad, pulsus paradoxus, electrical alternans, pericardiocentesis). For each question provide: 1. Correct answer 2. One-sentence explanation why correct 3. One-sentence explanation for each distractor Weight equally: 25% each topic. Include HKMLE trap answers (e.g., IABP for CS without knowing evidence, routine post-arrest PCI without STE). Base on Davidson's + AHA/ERC 2025 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.