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': 'Most serious form of Rickettsial disease - \nSelect and explain. \nA. Scrub typhus, B. Q-fever, C. Trench fever, D. Rocky mountain spotted fever', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. is \'d\' i.e.,Rocky mountain spotted fever "Among the Rickettsial diseases, Rocky mountain spotted fever is the most common and the most serious"The microbial chalonge "R rickettsii (causative agent of RMSF) is the most virulent Rickettsia" -- Clinical microbiology', 'role': 'assistant'}]