This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Anaesthesia
Nitrous oxide is contraindicated in all except 
Select and explain. 
A. Vitreo-retinal surgeries, B. Pneumothorax, C. Mastectomy, D. Laser surgery
C: Mastectomy
Answer: C: Mastectomy 
Explanation: Nitrous oxide is contraindicated in 

Pneumothorax, pneumoperitoneum
Vitreo-retinal surgery
Cochlear implant surgery
Intestinal obstruction
Laser surgery