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: Gynaecology & Obstetrics
What are the findings in USG, which suggests incompetent os:a) Cervical lengthb) External osc) Internal osd)  Funneling of amniotic sace) AP length of cervix 
Select and explain. 
A. abc, B. ad, C. bc, D. acd
D: acd
Answer: D: acd 
Explanation: None