Ans. D: Tension pneumothorax Tension pneumothorax is the accumulation of air under pressure in the pleural space. This condition develops when injured tissue forms a 1-way valve, allowing air to enter the pleural space and preventing the air from escaping naturally. Arising from numerous causes, this condition rapidly progresses to respiratory insufficiency, cardiovascular collapse, and, ultimately, death if unrecognized and untreated. Favorable patient outcomes require urgent diagnosis and immediate management.