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': 'Best confirmation for pregnancy at six weeks: \nSelect and explain. \nA. USG for cardiac activity, B. Doppler, C. estimation of serum beta-hCG, D. Bimanual palpation', 'role': 'user'}, {'content': 'Answer: A \nExplanation: In pregnant woman undergoing TVS Gestational sac :4 and half weeks yolk sac :5 weeks fetal node :5 and half weeks fetal hea :6weeks TEXTBOOK OF OBSTETRICS,SHEILA BALAKRISHNAN,Pg no:475,2nd edition', 'role': 'assistant'}]