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': 'Which of the following is an obligate parasite? \nSelect and explain. \nA. Mycoplasma, B. Chlamydia trachomatis, C. Gram -ve bacilli, D. Gram +ve cocci', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Chlamydiae is an obligate intracellular bacterial parasite.\nThey can be isolated only in cell culture.\xa0\nMcCoy and HeLa cell lines are MC cell lines used to culture chlamydia.', 'role': 'assistant'}]