This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Radiology Q Bank, Subject name: Radiology
20 years old male patient came to ER with severe dyspnoea. On examination, there is severe tachycardia, hypotension with distended neck veins. Chest x-ray is given below. Diagnosis is? 
Select and explain. 
A. Simple pneumothorax, B. Tension pneumothorax, C. Bullous emphysema, D. Bronchogenic cyst
B: Tension pneumothorax
Answer: B: Tension pneumothorax 
Explanation: Tension pneumothoraces occur when intrapleural air accumulates progressively in such a way as to exe positive pressure on mediastinal and intrathoracic structures. It is a life-threatening occurrence requiring both rapid recognition and prompt treatment to avoid a cardiorespiratory arrest. A non-tension pneumothorax is properly called a simple pneumothorax.