This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Kidney, Subject name: Pathology
Which is the most common risk factor for RCC? 
Select and explain. 
A. Urinary tract infection, B. Renal calculi, C. Smoking, D. Hypertension
C: Smoking
Answer: C: Smoking 
Explanation: Ref: Robbins Pathology, 9th ed. pg. 953Robbins states: "Tobacco is the most significant risk factor. Cigarette smokers have double the incidence of renal cell carcinoma".Risk factors for RCC:* MC risk factor: Smoking* Obesity (F > M), Hypertension, asbestos exposure, CKD, tuberous sclerosis* VHL (Von Hippel-Lindau syndrome): Around half to 2/3rd of the patients with VHL develop renal cyst and bilateral RCC.