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: Gynaecology & Obstetrics
[{'content': 'What is the finding seen earliest in USG : \nSelect and explain. \nA. Yolk sac, B. Fetal hea, C. Chorion, D. Placenta', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. is a i.e. Yolk sac Fetal structure Detected by TVS Detected by TAS Gestational sac 4 weeks 5 weeks Yolk sac 5 weeks 7 weeks Cardiac activity 5.1 - 6.5 weeks 8 weeks Embryonic movement 7 weeks', 'role': 'assistant'}]