A man brought into the emergency department after being stabbed in the chest. Chest is bilaterally clear with muffled heart sounds. BP is 60/nil. Pulse is 120bpm. JVP raised. What is the most likely diagnosis?

The key is B. Cardiac tamponade. [Chest is clear, so there is no pneumothorax or pleural effusion. Muffled heart sound is due to fluid in pericardial space, low BP from reduced chamber expansion due to pericardial fluid’s pressure and restricted right heart expansion causes raised JVP].