This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Miscellaneous, Subject name: Radiology
[{'content': 'Earliest ANC diagnosis on USG is done for? \nSelect and explain. \nA. Spina Bifida, B. Anencephaly, C. Lymphangioma, D. Nuchal edema', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. B. Anencephalya. The main sonographic feature of anencephaly is symmetric absence of the skull vault, and the cerebral hemispheres but relative preservation of brainstem and portion of midbrain.b. Although on ultrasonographically the diagnosis can be suspected by 12-13 weeks of gestation, it is more reliable by around 15-16 weeks, when the ossification in normal calvarial bones is more obvious.', 'role': 'assistant'}]