This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bacteriology, 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 diarrhoea", 'role': 'user'}, {'content': "Answer: B \nExplanation: Enterotoxigenic E.coli: Diarrhea caused by ETEC is of two epidemiological types Diarrhea caused by ETEC is endemic in developing countries in the tropics. Common in all age groups. Traveler's diarrhea: Adheres to the intestinal mucosa which is mediated by colonization factor antigens. Produces enterotoxin which may be heat liable or heat stable. Reference: Textbook of Microbiology; Anathanarayan and paniker's; 10th edition; Page no: 285", 'role': 'assistant'}]