This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anaesthesia, Subject name: Pharmacology
Nitrous oxide is contraindicated in patients with pneumothorax, pneumopericardium or intestinal obstruction, because it: 
Select and explain. 
A. Depresses an already compromised myocardium, B. Permits the use of limited FIO2 only, C. Is less soluble than nitrogen, D. Causes the expansion of air filled body cavities
D: Causes the expansion of air filled body cavities
Answer: D: Causes the expansion of air filled body cavities 
Explanation: Ans. (D) Causes the expansion of air filled body cavities(Ref: Goodman and Gilman 12/e p547)N2 O use is contraindicated in pneumothorax and volvulus because it may lead to development of high pressure in the closed cavities in the body (like obstructed loop of bowel, intraocular air bubble, a pulmonary bulla, pneumothorax, obstructed middle ear, air embolus, intracranial air and pneumoperitoneum).