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
Predisposing factors for skin cancer are – a) Smokingb) UV–lightc) Chronic ulcerd) Infrared light 
Select and explain. 
A. a, B. c, C. bc, D. ad
C: bc
Answer: C: bc 
Explanation: UV rays and chronic ulcers are predisposing factors for squamous cell carcinoma of skin.
Note -Cigarette smoking is predisposing factor for SCC of lips and oral cavity (but not skin).