This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Abortion, Subject name: Gynaecology & Obstetrics
A 25 yr. old comes in emergency with 2 1/2 months amenorrhea and abdominal pain and bleeding from vagina for 1 day. Her vitals are stable. On per speculum examination, mild bleeding is seen coming from the os. On per vaginal examination, the uterus is 10-week size, os is open and admits one finger. The most likely diagnosis is? 
Select and explain. 
A. Threatened abortion, B. Missed abortion, C. Inevitable abortion, D. Incomplete abortion
C: Inevitable abortion
Answer: C: Inevitable abortion 
Explanation: Ans. C. Inevitable abortionThe size of the uterus corresponds to the period of gestation, bleeding is mild, os is open, thus inevitable abortion.