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
Cervical dystocia is usually present at : 
Select and explain. 
A. Level of external os, B. Level of internal os, C. Level of isthmus, D. Level of cervical canal
A: Level of external os
Answer: A: Level of external os 
Explanation: Level of external os