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: Unknown
[{'content': 'Which one of the following is characteristic of microfilaria of W. bancrofti? \nSelect and explain. \nA. Cephalic space twice as long as broad, B. Excretory pore prominent, C. Nuclear column smudged, D. Caudal end uniformly tapering to a delicate point, and no terminal nuclei present', 'role': 'user'}, {'content': 'Answer: D \nExplanation: The features of microfilaria of W. bancrofti are: General appearance: Graceful, sweeping curves. Free cephalic space: As long as broad.\n\xa0\nExcretory pore: Not prominent:\n\xa0\nCaudal end: Uniformly tapering to a delicate point and no terminal nuclei present.\n\xa0\n5. Nuclear column: Nuclei discrete; Important points\n\xa0\nMicrofilaria of W. bancrofti and B. malayi in India display a nocturnal periodicity. Maximum density of Mf in blood is reported between 10 pm and 2 am.\n\xa0\nMan is the definitive host and mosquito the intermediate host of Bancroftian and Brugian filariasis.\n\xa0\nThird stage larva in mosquito is infective form.\n\xa0\nAdult worm may survive for 15 years or more.\n\xa0\nDuration of mosquito cycle (extrinsic incubation period) is between 10 and 14 days.\n\xa0\nMain vectors in India are: C. quinquefasciatus (C. fatigans) for Bancroftian filariasis and Mansonia mosquitoes for Brugian filariasis.\n\xa0\nPrepatent period: It is the time interval between inoculation of infective larvae and the first appearance of detectable Mf.\n\xa0\nClinical incubation period: Time interval from invasion of infective larvae to the development of clinical manifestations.', 'role': 'assistant'}]