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
In which case homologus artificial insemination is used in females: 
Select and explain. 
A. Hormonal disturbance, B. Tubal block, C. Cervical factor, D. All of the above
C: Cervical factor
Answer: C: Cervical factor 
Explanation: None