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': 'Rickettsiae -a) Multiply only within living cellb) Produce typhus fever of epidemic type onlyc) Transmitted by athropod vectorsd) Respond to tetracycline therapy \nSelect and explain. \nA. abc, B. ad, C. bc, D. acd', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]