This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Diagnosis in Obstetrics, Subject name: Gynaecology & Obstetrics
[{'content': 'Earliest of fetal heart can be detected at: \nSelect and explain. \nA. 6.0-6.5 weeks, B. 6.5-7 weeks, C. 7.1-7.5 weeks, D. 8 weeks', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. is a, i.e. 6.0-6.5 weeksRef. USG in Obs. and Gynae. Callen 4/e, p 119, 120When the question says--cardiac activity is earliest detected at--it means they are asking about TVS--Transvaginal sonography.On TVS, cardiac activity is seen at 6 weeks.Remember: If the question says cardiac activity is detected at and does not specify TVS or TAS: Then it is TAS--so then answer is 7-8 weeks.So earliest cardiac activity can be detected between 6 to 6.5 weeks.', 'role': 'assistant'}]