This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Diagnosis of Pregnancy, Subject name: Gynaecology & Obstetrics
[{'content': 'Gestational sac is seen by TVS at- \nSelect and explain. \nA. 5 weeks, B. 6 weeks, C. 7 weeks, D. 8 weeks', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., 5 weeks [Ref: Dutta's Obs 7th/ep. 68}TVS showso Gestational sac & yolk sac - 5th weeko Fetal pole & cardiac activity - 6th weeko Embryonic movements - 7th weeko Fetal gestational age is best determined by CRL between 7th to 12th weeks (variation +/- 5 days)o Doppler effect of ultrasound can pick up heart rate by 10lh week.", 'role': 'assistant'}]