This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Unknown
HCG doubling time is - 
Select and explain. 
A. 1 day, B. 2 day, C. 3 day, D. 3.5 day
B: 2 day
Answer: B: 2 day 
Explanation: Ans. is 'b' i.e., 2 day Human chorion gonadotropin (HCG)o It is secreted by the syncytiotrophoblast of the placentao Its main function is to maintain the corpus luteum of pregnancyo Its doubling time is 1.5 to 2 dayso Maximum level is reached at 60-80dayso Most sensitive for detection of Beta HCG is radio immunoassay-detects after 8-9 days of fertilizationo It disappears within two weeks of delivery from circulation.