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': 'Early date for detection of fetal hea : \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: 1st Trimester Scan: Assessment of Early Pregnancy and Fetal Viability: Gestational sac - 4.5 weeks, Yolk sac- 5 weeks, Fetal node- 6 weeks, Fetal hea- 6 weeks Reference: Dutta's Textbook of Obstetrics 7th edition page no 68", 'role': 'assistant'}]