This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Pancreas, Subject name: Pathology
A 65-year-old woman presents with a 5-week history of yellow skin and sclera, anorexia, and epigastric pain. Her past medical history is significant for insulin-dependent diabetes mellitus. She smoked one pack of cigarettes a day for the past 20 years. Physical examination reveals jaundice and a palpable gallbladder. Laboratory studies show a serum bilirubin level of 10 mg/dL, mostly in the conjugated form, and an elevated alkaline phosphatase (260 U/L). A CT scan of the abdomen discloses a mass in the head of the pancreas and multiple nodules in the liver measuring up to 3 cm. Which of the following is the most important risk factor for the neoplasm arising in the patient? 
Select and explain. 
A. Alcohol abuse, B. Cholelithiasis, C. Cigarette smoking, D. Diabetes mellitus type 1
C: Cigarette smoking
Answer: C: Cigarette smoking 
Explanation: Cigarette smoking is associated with a fivefold increased risk for adenocarcinoma of the pancreas. Cholelithiasis (choice B) and alcohol abuse (choice A) are associated with pancreatitis, not pancreatic adenocarcinoma.Diagnosis: Pancreatic adenocarcinoma