This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Virology (RNA Virus Pa-1,2 & Miscellaneous Viruses), Subject name: Microbiology
[{'content': 'Echoviruses are cytopathogenic human viruses that mainly infect the: \nSelect and explain. \nA. Respiratory system, B. Central nervous system, C. Blood and lymphatic systems, D. Intestinal tract', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Echoviruses are cytopathogenic human viruses that mainly infect the intestinal tract. Echoviruses were discovered accidentally during studies on poliomyelitis. They were named enteric cytopathogenic human orphan (ECHO) viruses because, at the time, they had not been linked to human disease and thus were considered "orphans." Echoviruses now are known to infect the intestinal tract of humans; they also can cause aseptic meningitis, febrile illnesses, and the common cold. Echoviruses range in size from 24 to 30 nm in diameter and contain a core of RNA.', 'role': 'assistant'}]