This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Gallbladder, Subject name: Surgery
All of the following are the risk factors for carcinoma gallbladder except: 
Select and explain. 
A. Primary sclerosing cholangitis, B. Porcelain gallbladder, C. Multiple 2 cm gallstones, D. Choledochal cyst
C: Multiple 2 cm gallstones
Answer: C: Multiple 2 cm gallstones 
Explanation: Risk Factors of Carcinoma Gallbladder Gallstones >3 cm Porcelain gallbladder Anomalous pancreatobiliary junction Choledochal cysts Adenomatous polyps Primary sclerosing cholangitis Obesity Salmonella typhi infection