This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Preoperative assessment and monitoring in anaesthesia, Subject name: Anaesthesia
Which of the following is the most significant risk factor for postoperative nausea and vomiting 
Select and explain. 
A. Female gender, B. Smoking, C. Age over 60 years, D. Surgery on the breast
A: Female gender
Answer: A: Female gender 
Explanation: Postoperative nausea and vomiting is most common in women, young people, and patients who have received opioids during surgery. Surprisingly, perhaps the one advantage of smoking is that smokers tend to have less postoperative nausea and vomiting than nonsmokers. Similarly, the incidence of postoperative nausea and vomiting is lower in the geriatric population.