This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General obstetrics, Subject name: Anatomy
At what level of b-HcG is it that normal pregnancy can be earliest detected by TVS (Transvaginal USG) : 
Select and explain. 
A. 500 IU/ml, B. 1000 IU/ml, C. 1500 IU/ml, D. 2000 IU/ml
B: 1000 IU/ml
Answer: B: 1000 IU/ml 
Explanation: Critical titre of HcG : For visibility of Gestational sac TVS -1000-1200 IU/ml TAS -6000 IU/ml Ref: Datta Obs 9e pg 601.