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 common presenting symptom of threadworm infection amongst the following is - \nSelect and explain. \nA. Abdominal pain, B. Rectal prolapse, C. Urticaria, D. Vaginitis', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Most patients infected of thread worm/pin worm/seat worm /Enterobius vermicularis are asymptomatic.\nMost common complaint: Perianal and perineal pruritus (pruritus ani)- nocturnal/early morning.\nOther complaints: Abdominal pain, irritability and restlessness.\nAll these symptoms caused by the female worms laying eggs on anal area.\nSevere infections: Sleep disturbances, neurosis, nail bite, grinding teeth at night.\nAdult worms can cause appendicitis.', 'role': 'assistant'}]