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: Dental
Fill the missing data in the common risk factor approach diagram. 
Select and explain. 
A. Diet and smoking, B. Smoking and disease, C. Smoking and prevention, D. Prevention and diet
A: Diet and smoking
Answer: A: Diet and smoking 
Explanation: None