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: Gynaecology & Obstetrics
[{'content': 'The protective bacterium in the normal vagina is: \nSelect and explain. \nA. Peptostreptococcus, B. Lactobacillus, C. Gardenella vaginalis, D. E. coli', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Vagina has inhabitant bacteria called as Doderleins bacteria which is a lactobaccilli, and converts the glycogen present in vaginal epithelium into lactic acid.\nThus, pH of the vagina is acidic\nThe pH of the vagina in an adult woman is 4 -5.5 with an average of 4.5.\nThe pH of vagina varies with age — for further details see preceding text.', 'role': 'assistant'}]