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: Microbiology
[{'content': "Regarding ETEC, true is - \nSelect and explain. \nA. Invades submucosa, B. Most common in children of developing countries, C. Fomite borne and person to person, D. Not a common cause of traveller's diarrhea", 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]