This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Stomach & Duodenum, Subject name: Surgery
[{'content': 'Malignant transformation is commonly seen in: \nSelect and explain. \nA. Stomal ulcer, B. Gastric ulcer, C. Chronic duodenal ulcer, D. Postbulbar ulcer', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. (b) Gastric ulcer* Malignant transformation is very rarely seen in gastric ulcer (<1%) - Not so common.* Giant gastric ulcer (>2cm) is associated with cancer in 6-15% cases* Of the above choices we can opt for choice B' only - but it is not so common.", 'role': 'assistant'}]